Oliver is a small and slender orange Tabby kitten with more long hair between his ears, three dark orange stripes on his back, and a white muzzle. About half-way through the film, he acquires a blue collar with his name and the address he lives at on a gold tag, thanks to his new wealthy owner, a kind and pretty little girl named Jenny Foxworth.
Oliver is brave, caring, friendly, kind, and cute. At one point, Dodger feels Oliver is disloyal to the gang since he tells them he wants to return to Jenny's house, where he is loved and has a comfortable life, instead of staying with them despite admitting that he likes his dog friends.
Despite his external goodness, he is capable of getting angry, mostly when he feels betrayed, such as when he gets conned by Dodger out of some sausages that he helped steal and, therefore, to which he thought he was owed some of them as compensation. He is also shown to be very loyal and protective of those he cares about, as he jumps from Fagin's cart onto Sykes' car and bites the villain's hand after he grabs Jenny.
Additionally, he is shown to be rather intelligent and resourceful. During the opening scene with Dodger, he climbs up onto a girder, walks across it, and jumps down onto a no-pass barrier while Dodger is busy looking behind him. Also, he manages to get on several vehicles during the scenes on the streets with his dog friends just as they do, proving that he is a considerably fast learner.
Oliver is first seen in a box in New York City on a street corner of 5th Avenue with eight other kittens who need homes, with the person selling them offering $5 for each one. The other kittens are bought quickly by several interested customers, be they children or adults, but Oliver is left in the box alone, even when the person lowers the price and then even offers to sell Oliver for free. One rainy night, after the seller has gone home to get some sleep and to get out of the storm, Oliver gets out of the box, after it gets filled up with water from a rain gutter next to it and torn into pieces due to the cardboard design getting so waterlogged, almost sending Oliver into a storm drain. After nearly getting splashed from a passing car hitting a large puddle of rainwater as it roars down the street, scaring him, Oliver flees to find a dryer spot in an alley to sleep, but then, he comes across some vicious alley dogs who begin to chase him. Still, he manages to escape by jumping over a big chain-link fence where he finds a dry place to sleep on the top of a Ryder rental truck's rear wheel.
The next day, when Oliver hears the truck starting up and the tire he's on jerks backwards as the truck shifts gears to drive off, he jumps off and goes off to explore New York City. When Oliver hears some hip hop music from a black man's radio and sees him dancing, he tries to dance along for a while. Then, he tries to find some people who "might" adopt him, but no one seems to notice him at all. He soon meets a little boy who is about three years old and begins to play with him. The boy's mother pulls him away, telling him that he can play with Oliver some other time. He follows the little boy and his mom while crossing the street, without noticing, but then, Oliver gets scared by the cars, their honking noises, and the people crossing towards his way and runs back on the sidewalk. Later, Oliver smells hot dogs, which are being sold by a guy named Louie. Oliver's first two attempts to procure hot dogs are unsuccessful, but they end up attracting the attention of a dog named Dodger. Oliver meets Dodger, who offers to help Oliver. Oliver refuses at first, along with initially being hostile when he sees Dodger for the first time until he is assured that Dodger will not try to make a meal out of him, and after teaching him a few lessons and a few things he knows about Louie. Dodger asks Oliver if he "feels that rhythm." After a jackhammer does its job, Oliver does "feel it" and accepts Dodger's help. Dodger begins, while pretending, to chase Oliver, which distracts Louie and allows Dodger to get the hot dogs while Oliver escapes, squirting mustard all over Louie's face, much to Louie's annoyance and frustration. When Oliver meets up with Dodger again in a construction site, Dodger reveals that he conned Oliver and had no intention of sharing the hot dogs with him, forcing him to give chase for his meal while Dodger sings "Why Should I Worry" as they head through the streets of Manhattan towards the river.
Oliver secretly follows Dodger to his barge home in an area that had been condemned by the Port Authority of New York and New Jersey due to the urban decay on the pier, where he climbs up onto the roof and listens as Dodger gives his dog friends: Francis, Rita, Tito, and Einstein, the hot dogs and tells them the story about how he got them after they ask him to do so. Dodger describes every event that occurred during the day, then he describes Oliver as a "greedy, ugly, psychotic, monster with razor-sharp claws, dripping fangs, and 9 lives, all of them hungry coming right at him with burning eyes," but before he can finish the story, Oliver falls from the roof due to some rotted timbers, covered in a piece of cloth, and into the barge where the gang runs off in fright, thinking he's a monster. At first, they don't know what it is hiding under the cloth. Tito thinks it's an "alien" when a mysterious paw, coming out of the cloth, grabs and scratches him on the nose, but then when the result is out, and it turns out to be Oliver, referred as a cat by Rita after seeing the result and telling everyone to calm down and what it is, they soon become infuriated at him. Just as the gang (except Dodger) is surrounding Oliver and asking him questions about how and why he came to their place, intending to attack him for trespassing, Oliver reveals to them the truth about his involvement with Dodger's scheme and Dodger admits to his friends that Oliver assisted in stealing the sausages, developing respect for the kitten. The gang treats Oliver as a friend, with Rita assuring Oliver he's safe with them now since Dodger vouched for him.
The gang starts to mock Dodger's "monster" story and then, a dogpile "fight" game begins before a voice is heard, frightening Oliver a bit and causing him to hide in a "loot" box. Then Fagin, the owner, whose voice Oliver heard and was frightened of, comes in, tells his dogs to stop, and receives a warm welcome home from them. When a honking noise is heard outside, Fagin knows it means his evil boss, the loan shark Mr. Sykes, whom he owes money to, is here to collect Fagin's debt. Fagin is disappointed by the "loot" his dogs brought for him to pay back Sykes and he discovers Oliver, but before he can examine him, Sykes' two Dobermans, Roscoe and DeSoto, come in and shoo him out to talk with their master. Then, DeSoto sniffs out Oliver, while Roscoe's taunting the gang. However, after Sykes signals them that it's time for them to go, DeSoto tries to eat him, but Oliver manages to scratch him on the nose, to which the two dogs try to attack him, but Dodger and the gang manage to stand in front of Oliver and protect him and shoo the two evil dogs away, to which Roscoe says that Dodger and the gang will pay for what they've done, starting with Oliver. After the Dobermans leave, Dodger assures Oliver he can "really pick 'em" and pulls a high-five paw trick on him.
Then, Fagin walks in all wet (after falling off the pier from being startled by Sykes blaring his horn) and sad since he was given only three days by Sykes to pay him back or else who knows what might happen to him, his home, and his dogs. Later, Fagin says he saw DeSoto's nose and wondered who did it, after being cheered up by his dogs, and is proud that it was Oliver, revealed by Dodger. After Fagin accepts Oliver into the gang and reads a story, to which he was reluctant at first and then, cooperative after hearing and seeing Einstein sad, to the dogs and cat, Dodger turns off the lights, hops on his bed, and goes to sleep. Oliver, who is napping on Fagin's lap, looks at him, runs to his bed, and snuggles beside him. At first, Dodger can't understand, but after watching Rita, who is half asleep and who witnessed Oliver rushing over to him, and Oliver smile, he quickly understands that the kitten loves him, then falls asleep. Rita does as well. Dodger smiles and curls beside him. Oliver does this to show that he likes Dodger.
The next day, after Fagin leaves Dodger responsible for Oliver, who along with the gang is riding in Fagin's scooter, and then tells the gang to go out and search for food while he finds a way to earn or even steal money to pay off his debt to Sykes, Oliver agrees to help the gang with their master's problem. He is then given a lesson by the gang, mainly Rita while singing "Streets of Gold", about the rough, tough streets of New York and about "how the best survive by keeping their dreams alive." During and after the song, Oliver is chased by a vicious alley dog and then, is rescued by the gang yet again, as Dodger, Tito, Einstein, and Francis scare the alley dog away by growling at him together, showing that the dog would have to go through them to get to Oliver, sending it whimpering and yelping back up the street in fright. Oliver even tries to "bark" like a dog to shoo the alley dog away and the gang finds it amusing a bit.
When Dodger notices a limo round the corner up ahead and heading their way, he has an idea on how to steal its radio so as to help Fagin with his financial problems. As part of the plan, he assigns Oliver as someone to help Tito, who will handle the stealing of the radio, during the operation. In the car, while the driver (Winston) is out tending to Francis, whom he supposedly bumped into when it was actually Einstein who did the bumping, Oliver asks Tito some questions, which begin to annoy him a bit. Tito, despite being annoyed, asks Oliver to be the lookout while he takes out the wires of the radio. Oliver doesn't know what it means so he asks him another question. Tito answers him by telling him to look out the window and "see if it's still daylight." While looking outside, Oliver hears, turns his head, and sees something in the back. Feeling a bit scared, he informs Tito, but Tito is too busy with the last wire. Before Oliver can continue, he slips on the keys, which were still in the ignition, causing the car to start up, thus electrocuting and sending Tito "flying" out of the car, and Oliver gets his paw tangled in one of the severed wires.
Luckily, a little girl named Jennifer "Jenny" Foxworth, who was the one Oliver saw sitting in the back, comes to his aid, and unties him instead of harming and shooing him away, just as Winston returns to the driver's seat to see if Jenny is okay. Later, he is taken to her upscale mansion on 5th Avenue, with Dodger and Tito in pursuit. Winston, the driver and Foxworth family's butler, is against the idea of Jenny adopting Oliver for the reason that they have a dog: a pedigree poodle named Georgette. Winston was left responsible for Jenny by her parents while they were away on business in Europe, and they have to wait for her parents' approval. In the kitchen, Oliver has a special meal prepared by Jenny, who made a mess in the kitchen while preparing the meal, which annoys Winston a bit. When Georgette enters the kitchen, despite Winston's warning, she is shocked and disgusted to see a cat in the house and eating out of her bowl. Calling for Winston fails, so now, Georgette does everything she can herself to handle Oliver with sarcastic questions and finally a scold, telling him that despite the fact Jenny's family owns the house, she is the person with the most power in the household. Luckily, Jenny comes in after having had a talk with her parents on the phone and tells Georgette that they have approved about her decision of keeping Oliver and that they're going to be "the best of friends." Georgette simply smiles and chuckles slyly after hearing it.
Meanwhile, back on the street, Dodger and Tito come back to Fagin and the rest of the gang and inform them about everything, thinking Oliver is in "danger" and being "tortured." Dodger comes up with an idea on how to "rescue" Oliver.
A little while later, Oliver and Jenny are in the practice room where Jenny always practices piano lessons. As Jenny begins to do so, after being reminded by Winston, Oliver somewhat helps her by playing a discordant note. Then, Jenny sings "Good Company" while playing the piano with Oliver. Later, Oliver and Jenny spend the rest of most of their fun of the day at Central Park, including riding in a small boat in the lake, playing with fences, greeting people they pass by, eating strawberry ice cream, riding in a horse carriage, and finally, buying Oliver's things with his name on them in a shop, including his bowl and finally, of course, Oliver's new golden blue-collar name tag with his name and the address on it. Oliver is so happy and excited that he jumps on Jenny and licks her to show that he's grateful, happy and that he loves her very much. At night, as Jenny is getting ready for bed while singing a few words from "Good Company", Oliver jumps in as well to sleep with her, nuzzles his nose with Jenny's as she picks him up, is tucked in, and is told "Good night, Oliver." Winston turns off the lights and closes the door with a warm smile on his face.
The next morning, while Jenny is at school, Dodger and the gang arrive to launch their "rescue mission." When they see Winston is banging on something with a rolling pin, they think he's "torturing" Oliver. Winston is distracted by them, mainly Einstein and then Francis, and left outside.
When they come to Georgette's room, she thinks they're after her, and she's disgusted by them, especially Tito, who has taken a sudden "love" interest in her and tries to call Winston, but when Dodger mentions that "we'll leave as soon as we get our cat," Georgette is cooperative for the reason that she's a dog, and some dogs hate cats, and she's been jealous of Oliver ever since she first laid eyes on him and he set foot in her house. She had hoped to get rid of him in some way. Later, Oliver is seen sleeping with joy on his pillow in Jenny's room. Rita is the first one who seems convinced that he's okay but, Georgette, eager to get rid of him, persuades them that "he's so traumatized" and when Winston's voice is heard again, she hands him to them in a pillow sack held by Einstein and Francis and allows them to flee through the fire escape, though Oliver is startled awake when Georgette grabs him and is left wondering what is going on as the gang escape with him back to Fagin's barge.
The gang brings a confused Oliver back to Fagin, but Oliver becomes upset upon discovering what happened when he realizes he has been taken away from Jenny. This angers Dodger, who accuses Oliver of looking down on him and the other dogs as "the riffraff." Dodger's wrong because, to tell the truth, Oliver admits he really loves his friends, but when it comes to having a new home, things get a bit complicated, especially when being taken away from it. Despite still being upset, Dodger allows Oliver to leave. Oliver leaves with great sadness and sorrow, but not before Fagin returns and takes him back in. After noticing Oliver's gold collar and its address, Fagin has an idea for ransoming him to get the money he needs to pay back Sykes.
At night, at Sykes' warehouse, Fagin goes over his plan of ransoming Oliver before entering the warehouse, pretending that Dodger is Sykes. Oliver is taken in where Fagin discusses his plan with Sykes. Fagin, at first, discusses it awkwardly, causing Sykes to lose his patience and snap his fingers to order his Dobermans to attack him, but not before Dodger jumps into the scene and fights them off while Fagin discusses his plan properly and loudly this time and showing him Oliver as proof. Sykes snaps his fingers again to order his dogs to cease the attack. After Sykes notices the collar and the address on it, he's convinced. He pets Oliver tells Fagin that he's proud of him because he's "starting to think big," and gives him 12 hours left as his "last chance" to pay him back while feeding dog biscuits to his dogs while Fagin and Oliver come to Dodger's aid after he is left lying injured and unconscious and having received severe (but invisible) injuries from the attack.
Later, at night, Jenny follows the map she was given along with the ransom note by Fagin earlier in the day (unknown to her) with Georgette in order to meet him at the rendezvous. She appears lost when, in reality, she has arrived at the right place upon meeting and asking for directions from Fagin. Fagin and Jenny have a small conversation, not knowing that Sykes and his dogs are watching them in his car from a distance. Fagin finds out who is Oliver's "rich cat person owner," as Jenny brought some small change in her piggy bank as payment for getting Oliver back. After seeing Jenny burst into tears, Fagin is left with a hard decision about whether to follow his good heart or not and feeling guilty to see Jenny and Oliver sad.
Finally, Fagin follows his good heart by giving up, pretending to find Oliver in a box, and giving him back to Jenny. However, Sykes then makes his move, snatching Jenny, tossing Oliver out, and telling a shocked Fagin to keep his mouth shut and to consider their account closed, as he intends to ransom Jenny to get the money Fagin owes him. Then, Dodger and the gang come to Oliver's aid after having been tossed out the window and his mistress Jenny kidnapped by Sykes. Dodger assures and promises Oliver that they will "absitively" get her back. Then, Oliver and the dogs run off to Sykes' warehouse, only without riding in Fagin's scooter this time.
At Sykes' warehouse, after an inspection made by Tito and Francis that discovers everything is locked up tight, Dodger comes up with a plan on how to get in, including Oliver as part of the plan. The plan is set with Oliver in a football helmet as the second "cannonball" on a "seesaw," Tito the "maestro," and Francis as the first "cannonball." After Francis jumps, Oliver, in the helmet, is launched and breaks through a window. The noise of the glass shattering alerts Sykes and his dogs. After Oliver lands safely inside, he hears the Dobermans and hides in a corner in order to avoid being detected by them, then he manages to open a hatch that could only be opened from the inside and lets the dogs in. As Oliver and the dogs enter, they do everything they can to avoid security cameras and Sykes' dogs (who were also alerted by Georgette's scream because of a broken nail when she entered the place).
From the top of Sykes' office, Oliver and the dogs observe Sykes talking on the phone to Winston for the ransom and see that Jenny is okay, but tied up. Dodger comes up with a plan on how to distract Sykes and help Jenny. The Dobermans are later alerted by their enemies' smell. While Tito, Francis, and Einstein distract Sykes by posing as a pizza delivery guy and luring him away, Oliver and the rest of the dogs enter and try to rescue Jenny. Oliver and Jenny are happily reunited. The rest of the gang shows up after having distracted their enemies, thanks to Georgette dropping a heavy tarpaulin on Roscoe and DeSoto to buy them time to save Jenny.
Chewing the ropes off Jenny fails and their enemies return, before Dodger has another idea to get them out of here with a crane and Tito, who is at first reluctant, then cooperative with Georgette's persuasion, as the mechanic. They manage to escape with Jenny before Sykes and his dogs break down the door, which the gang locked up earlier. Things go well until Sykes cuts off the controls of the crane with a fire ax, causing Oliver and the rest to fall and land on a long slide. They slide until they reach the end where, unfortunately, their enemies have them cornered.
When all seems lost, and before Sykes can snap his fingers to order his dogs to attack, they hear a honking noise and breaking in through the window, it turns out to be Fagin with his scooter. Oliver and everyone else jump in and drive away as fast as they can. They seem to be able to outrun the two evil dogs, but not before Sykes manages to catch up with them in his car. Fagin, having no choice, drives his friends into a subway station, but Sykes, driving like a madman, is able to drive in as well. Fagin then drives them through a tunnel with Sykes still in pursuit. When Sykes' car collides with Fagin's scooter by ramming it, Jenny falls and ends up on Sykes' hood. When Sykes tries to grab her, Oliver jumps to his car and bites his hand, but still biting his hand, Sykes throws Oliver in the backseat where Roscoe and DeSoto are. Then, Dodger comes to Oliver's rescue, fighting off Roscoe, killing him by pushing him out, while breaking through the back window, and letting him slip while holding on to Dodger's scarf for a few moments, before falling on the subway tracks and being fatally electrocuted by the subway's third rail. Just as DeSoto is about to kill Dodger for revenge, Oliver jumps on DeSoto and scratches him, causing DeSoto to yelp in pain, jump, and fall to his death as well on the subway tracks. When DeSoto jumped before dying, Oliver is seen almost falling to the same fate, but not before Dodger saves him again. On the Brooklyn Bridge, when Jenny is calling for Fagin's help, Fagin comes to help her while Tito takes command of his scooter. Sykes manages to grab Jenny's leg and pull her back in, just before Oliver and Dodger jump on him and fight him off, allowing Jenny to jump to Fagin on his scooter.
In front of them, a subway train is coming their way. Tito is capable of saving everyone by jumping on one of the cables of the bridge and driving them to the top, but Oliver and Dodger are still in the car, fighting Sykes. Sykes throws Oliver and Dodger off of him before he notices the train heading his way and the train kills him, sending him and his car into the East River. When the rest of the company drive back down, Jenny runs to search for Oliver, only to find a sad Dodger approaching her from the maintenance path next to the subway tracks, holding a "thought to be dead" Oliver. At first, everyone believes he's dead, but when Jenny hears a soft meow from Oliver, she quickly realizes that Oliver is alive and everyone rejoices, except Georgette, who is still in great shock from the chase. Then, Dodger and the rest of the gang are accepted as Jenny's new best friends.
The next day, at Jenny's home, Oliver and his friends are celebrating Jenny's 8th birthday and giving her birthday gifts. When it's time to go, the gang (except Tito) say their good-byes to Oliver and vice versa. Before leaving for home, Dodger asks Oliver if he just wants "to hang out or anything." Before finishing, Tito runs away from Georgette after having been given a bath and dressed into something classy by her and he says goodbye to Oliver before running after the rest of the gang who took off after Fagin as he drove off on his scooter. After that, Dodger asks Oliver if he can "handle the champ." Oliver replies "sure" and pulls the same high-five paw trick on him as Dodger did before. Dodger says he's "okay... for a cat" and that he and the gang will "keep a spot open for ya in the gang... vice president, uptown chapter" and then says his goodbye to Oliver. And then, Dodger sings the "Why Should I Worry" reprise, only this time with the gang singing along with him, while Jenny, Winston, and Oliver say their good-byes to them and watch them go. Then, Dodger and the gang join Fagin in his scooter while still singing on their way back home through gridlocked Manhattan traffic.
Oliver made regular guest appearances in House of Mouse. His most notable appearance is in "Max's Embarrassing Date", where he is sitting at a table with Dodger, as Goofy's being tipped over, causing a mess to everyone at their tables. He can also be briefly seen along with some of the dog-gang members in the opening theme, being petted by Mowgli.
Oliver made numerous appearances at the parks with Dodger, Jenny, Tito, Francis, and Georgette in the years following the movie's release. He was retired in the late 1990s but appeared with Dodger at the grand opening of Hong Kong Disneyland in 2005.
- Oliver isn't actually named Oliver until Jenny buys him his collar. Jenny is the only one in the movie whoever calls him Oliver - otherwise, he is called "kid", "kitty", or "cat". One interesting note is that Jenny actually calls Oliver by his name once before buying his collar. However, at the end of the movie, Francis and Tito refer to him as Oliver.
- Unlike the other kittens from the beginning of the movie, Oliver is the only cat with more long hair between his ears and three dark orange stripes on his back.
- Oliver is the sixth main protagonist whose film is a musical, but who does not sing any number; the other three are Peter Pan, Arthur Pendragon, Robin Hood, Tod, and Basil. Of course, Arthur does sing with Merlin, but it's all simultaneous, whereas Robin sings acapella to the tune of "Rock-a-Bye Baby," but neither sings a number alone. Oliver, on the other hand, does not sing at all, making him the second not to sing in a musical, period, Basil being the first in this case (though he is heard humming to himself at some point).
- Near the beginning of the movie, when Oliver climbs out of the gutter during the rainstorm, the "Kitties Need Home" sign is visible in the close-up, but disappears in the wide shot. Also, Oliver moves from near the curb to a few feet in on the sidewalk.
- In "Why Should I Worry", Oliver jumps out of the wet cement onto the sign that says "Wet Cement", with no cement on his front paws. Shortly after, he jumps down off the sign, and he has cement on his paws.
- Throughout the movie, Oliver is sometimes shown to have either orange eyes matching his fur color or green eyes.
- During Jenny's birthday, Oliver is seen wearing a birthday hat but then it disappears from a distant then later, reappears again after a close-up.
- When Oliver pulls the same high-five paw trick on Dodger as the former did before, his collar disappears but reappears again after a close-up. The same thing happens in some scenes during the subway chase.
- To promote the French release of "Oliver & Company" in 1989, Anne Meson made a song about Oliver called "Oliver", which was a hit in France . Between 1989 and 1992, Oliver (alongside Dodger, Tito, and Francis) was featured in a series of music videos interacting with her. During the inaugural year of Disneyland Paris' (then "Euro Disney") in 1992. She performed the song at the park alongside Oliver and Dodger.