Lewis was derived from the original A Day With Wilbur Robinson storybook as a friend of Wilbur that served as the narrator as he visited his friend's large and strange home.
Born in 1995, Lewis is a 12-year-old boy incredibly gifted boy in terms of intelligence. He loves to invent and has been doing so since he was young. While a generally kind kid who has good intentions, he can also let frustration cloud his mind. He easily becomes discouraged when his inventions don't work or he begins to think about how he is almost a teenager and still an orphan. He is also somewhat careless and selfish as he knowingly keeps his roommate, Goob, up all night working on his project and completely ignores his suffering and never appeared to show any signs of remorse for indirectly ruining his future.
He is also frequently caught up in the past, longing to go back and change his life so he won't be an orphan. By the end of the film, however, Lewis learns to keep moving forward and embrace his failures. He has also shown to accept others for who they are, as shown when he first acquainted to the frog and music lover Franny during the Science Fair. This kindness was what enabled the Robinson family to expand later.
As an adult of 42 years, Cornelius Robinson is highly passionate in his inventions to improve the lives of humankind. As a result, his pure dedication and charisma were what led him to be highly regarded as "Father of the Future" and "Inventor Extraordinaire'. He has also shown to let go of his past, thus coining the phrase "Keep Moving Forward" as his motto.
However, Cornelius has shown to turn a blind eye on his failed inventions. This is shown when he had the failed DOR-15 shut down but not completely as the Helping Hat managed to escape from the prototype room later. This nearly became his undoing and downfall as he was unaware of her escape due to him being on a business trip for a few days. However, his younger self managed to avert this (save for the missing second-time machine) just before Cornelius comes back home by the near-ending of the film.
His outfit consists of a white short-sleeved collared shirt, blue sweatervest, red shorts, white kneesocks, brown shoes, and glasses.
An orphan, Lewis was abandoned by his mother at the Sixth Street Orphanage when he was an infant in 1995. Because of his inventing hobby, he has scared off over 124 possible parent pairs and causes some difficulties for his roommate, Goob. After another adoption interview ends in disaster, he begins to lose hope of ever being adopted. He eventually figures that his mother may have only abandoned him as she wouldn't be able to take care of him and tries to find her identity by building a Memory Scanner, a device that scans people's deepest memories. Presenting his machine at the Joyce Williams Elementary School Science Fair, he runs into Wilbur Robinson, who claims to be a time cop from the future and warns him of a man with a bowler hat's plans to sabotage things. Lewis doesn't believe him and thinks him to be crazy. The Memory Scanner is sabotaged by Bowler Hat Guy's robotic hat DOR-15 when Lewis tries to present it and in the mayhem caused by the machine's malfunction, Lewis retreats to the roof of the orphanage in sorrow. He's soon confronted by Wilbur, who tries to get Lewis to return to the science fair and fix the Memory Scanner. In an attempt to convince Lewis he's really from the future, he takes him to his home time in 2037 with the Time Machine. Wanting to use the Time Machine to try and find his mother, it ends up crashing into the hills near Anderson Observatory. Wilbur tells Lewis he needs to fix it, agreeing on the condition set by Lewis to see his mom, but actually lying.
Upon arrival to the garage and meeting Carl, the robot runs off in terror. Wilbur places a Carmen Miranda style fruit hat on Lewis' head to hide his hair, a dead giveaway for him being from the past. While Wilbur is off to calm Carl down, Lewis takes a Travel Tube to the Robinsons' front yard. Frightened by Lefty at the door, he runs into Wilbur's grandfather Bud. Trying to search for the garage and Bud's teeth, Lewis meets the rest of Wilbur's family. While meeting Franny in her music room (and helping the Frog Band rehearsal with maracas), he finds Bud's teeth in Frankie's mouth. Sneaking out while the rest of the family comes in to congratulate Bud, he bumps into Wilbur, who drags him off to ask what he's learned about the family and tells him to get started on fixing the Time Machine. Wilbur gives Lewis the "pep talk of the century" as he explains his father's motto of "Keep Moving Forward" and the struggles in actually building the time machine (as well as giving Lewis a different hat). After a failed effort to get the Time Machine started, Lewis becomes very frustrated about his capabilities and the Keep Moving Forward mantra. Wilbur tries to comfort him, but Lewis believes he's simply no good.
The boys are then called to dinner and have to go out of fear that Franny will come and discover the time machine. Lewis enjoys dinner with the Robinsons and is asked to fix a PB and J invention that looks like one he had tried to create earlier, but fails and splatters everyone with peanut butter and jelly. To his surprise, the family congratulates him on his "brilliant failure" and he admits that if he had a family, he'd like them to be just like the Robinsons. Later, Tiny the dinosaur attacks Lewis, trying to capture him, and the family rushes to defend him. Wilbur is nearly eaten while trying to save Lewis, so Lewis grabs a shovel and uses one of the springy plants in the garden to jump into Tiny's mouth and tries to rescue Wilbur. He nearly fails, but Wilbur finds Gaston's Meatball Canon in Tiny's mouth and uses it to shoot Mini-Doris off of Tiny's head, ending the battle. The boys celebrate, with Lewis commenting on how great a team he and Wilbur make. Lewis is surprised that the Robinsons risked so much to protect him and Franny after he accidentally calls her "Mom," offers to adopt him, which he happily accepts. However, Wilbur decides that he can't keep up the act any longer and knocks off Lewis' hat, revealing his hair to the shocked Robinsons. Franny takes back her offer, leaving Lewis heartbroken and Wilbur blurts out that he never actually intended to take Lewis to see his mom. Upset and betrayed, Lewis yells at Wilbur, shocked that he was dumb enough to believe he and Wilbur were friends and runs off.
While sitting in the garden crying, the Bowler Hat Guy appears and offers to take him back to see his mom if he fixes the Memory Scanner. He agrees and goes with him despite Wilbur's pleas not to. Lewis fixes the Memory Scanner and explains its operation at which time Bowler Hat Guy double-crosses him, revealing that Lewis is, in fact, Cornelius Robinson; Wilbur's dad, and the man who invented Doris. He then reveals himself as an older Goob, Lewis' old roommate who lost a baseball game due to Lewis keeping him up all night and grew so furious over it that he wanted revenge. Lewis apologized to Goob for unknowingly messing up his life but tells his old roommate that it was mostly because he was obsessed with his past when he should've let go and "keep moving forward", incidentally coining his own future phrase. However, Goob finds it easier to blame Lewis than take responsibility for his own life. Goob prepares to depart in the time machine when Lewis escapes with the help of Carl and Wilbur and reveals that he knows the truth about everything. But before they can get back to the house, but they are attacked by Doris who destroys Carl and steals the Memory Scanner. Wilbur pleads with Lewis to fix the time machine and history, but Lewis lacks the confidence to do it, saying they should call his future self, but Wilbur calls Lewis "Dad" and tells him he's the only one that can do it. The change in the timeline then causes Wilbur to be erased from existence.
Lewis finds the Robinsons mind-controlled by Doris hats in a world where Doris rules and discovers what happened from the Memory Scanner records which show she eventually betrayed and killed Goob. Chased by the Robinsons, Lewis manages to fix the time machine and escape. As he is chased by an enormous Doris and eventually by a small swarm of hats, Lewis starts to beat himself up for having invented Doris in the first place before having an epiphany and travels back to where Goob is about to sign a contract with Inventco, where he reveals Doris' planned betrayal. Lewis promises never to invent Doris, erasing her from existence and takes Goob to see the future she created, which turns back into the original future. After Wilbur is restored, Lewis convinces him to get his family to adopt Goob, but Goob runs away, leaving behind his binder with a question mark next to what he wants to do next. He is reunited with the worried Robinson family and reveals that this experience has caused him to feel better than he has in a long time. He then meets his future self who arrives home early and shows him all of his inventions, revealing that the Memory Scanner is their first real invention and the one that led to this great future. Seeing this causes Lewis to regain his confidence in going back to his own time and showing the Memory Scanner and he asks Cornelius if he ever does meet his real mom, to which Cornelius simply tells him to go back to the Science Fair and find out for himself. Lewis says goodbye to the family, getting advice from Franny and Wilbur reminds him before he leaves that he will see the Robinsons again as they are his family after all.
To Lewis' surprise, Wilbur takes him to see his mom like he promised rather than to the Science Fair. Lewis goes to stop her from leaving him, but realizing that he already has a family, the Robinsons, Lewis stops himself and slips on a step, scaring his mother and causing her to run away, forgetting to knock on the orphanage door, so he knocks on the door himself, and watches from the time machine as Mildred finds his infant self.
Returning to his time, he explains to confused Wilbur that he doesn't need his mother as he already has a family. He then hugs Wilbur who expresses his surprise that Lewis ended up being both his dad and best friend. Wilbur gives Lewis his taped back together plans for the Memory Scanner and promises to return if Lewis screws up the future again. Lewis watches as Wilbur returns to his time and sky-writes "see ya later, Dad."
Lewis returns to the Science Fair, but remembering Goob, rushes to the baseball field and wakes him up, allowing him to catch the ball, winning the game and guaranteeing Goob a better future. At the fair, Lewis convinces Mr. Willerstien and Dr. Krunklehorn to let him try the Memory Scanner again and uses Dr. Krunklehorn as his test subject as he no longer needs to find his mother. He plugs in the date of her wedding and the Memory Scanner shows the event perfectly, and, to his shock, reveals that she is Grandma Lucile from the future. Bud arrives and calls Lewis a special kid, saying he doesn't look like a Lewis to which Lewis replies he's told a lot that he looks more like a Cornelius. Lewis wins the Science Fair and meets young Franny who tells him she believes that frogs have more musical ability than people and people think she's crazy for that. When Franny demands to know if he thinks that too, Lewis, remembering Franny's band in the future and her telling him that she's "always right," tells her that he thinks she's right, endearing him to her. A reporter asks for an interview and Lewis, seeing his future parents and wife realizes that he faces a great future. Lucile and Bud adopt Lewis and nickname him Cornelius. On his way out, Lewis says goodbye to Goob, who, no longer the bitter man he became in the future, is adopted by a couple, and also says goodbye to Mildred. Lewis and his new parents move into Anderson Observatory which becomes the future Robinson house and Lewis turns the dome into his lab and sets to work on building Carl.
Lewis only makes brief appearances in the Meet the Robinsons video game, with Cornelius sending a videophone message to Wilbur at the start of the game to stay out of trouble and a brief appearance as a child at the Science Fair.
Lewis appeared as a walkaround character when the film was first released at Disney's Hollywood Studios and Disney California Adventure. Ever since, he has become rare, though can still be found as a random character in Hollywood Studios.