Role in the film
Calvin Wheeler is seen preparing for school. While leaving, his parents ask him to take out the trash but instead he has a couple of guys (and somewhat "friends" of Calvin) named Leonard and Thrash do it instead; much to their disapproval.
When Calvin returns home at night after a basketball game, they are very disappointed with Calvin's low grades on his report and about his lack of responsibility and his habit of taking shortcuts.
A few days later, Calvin tricks his mother into signing some adoption papers for a dog named Tyco, which he intends to adopt and use to win $5,000 1st prize in a dog show at the Bedford Civic, in which the next one is in two weeks from now in order to use $3,000 from it to buy the last Gotham Man comic he needs, since his parents won't allow him to have a pet (not even a goldfish).
The next day, when Calvin's mother arrives home and after Calvin and his best friend, Raymond Figg a.k.a. Figg get themselves cleaned up from all the mud (since Tyco tried to do the same to Calvin's enemy, Preston Price earlier in the day) and later, start to have fun when playing with the water hoses altogether, they manage to hide Tyco in the small pool.
In the morning, when Calvin leaves for school and forgets to feed Tyco, Tyco decides to enter the house and start eating all the food he can find in the kitchen and fridge while causing a huge mess. When Calvin returns to find the kitchen messed up, he tries to catch Tyco until he finds his parents having arrived home early, so, he tries to hide Tyco under a cover and takes the blame and responsibility; much to his parents' shock and yet astonishment when they see that their son didn't make any excuses, didn't blame anyone else, and finally took responsibility for anything as he usually does. Calvin then takes Tyco to his room without getting caught. After cleaning up the mess, he finds Tyco having chewed on his sneakers and eating his geometry homework and scolds at him. His scolding almost gets him busted with his mom until he tells his mom that he's "just doing his nightly meditations."
The next day, after Tyco breaks free from and with the tree he is tied to on a leash by Calvin for the mess he caused, breaks through the fence, and rescues Calvin from Leonard and Thrash, the two would-be trouble makers, Calvin's parents are amazed to see their son spontaneously doing work around the house without even being told when they watch him fixing the gate.
Later, Calvin's secret about Tyco is out when he and Figg find his mom home early and having found and barricaded "a bear" in his room. When she tries to call 911, Calvin finally reveals the truth. After his parents have a long discussion at night about Tyco, they finally accept Tyco since having a dog was proven to be something good for Calvin and that "love doesn't have any shortcuts." However, Calvin is punished with no T.V. or cellphone for 2 months due to tricking his mother into signing the adoption papers for Tyco and is told to improve his grades at school.
The next day, after Calvin and Tyco win the Royal Hound's Obedience and Obstacle Dog trial, Figg arrives and finds posters of Tyco on the streets; claiming he is "a lost dog named Chester already belonging to a family", thus, forcing Calvin to give up Tyco to his "family". Calvin asks Figg to take down the posters but he refuses. Then, Calvin takes Tyco back to his real "family", refuses the reward money, and asks them to take care of him; much to his reluctance. Even his parents appear disappointed despite telling him to do the right thing.
On the day of the Royal Hound Top-Dog finals, after Calvin, Figg, and Emily Watson realize it was all a trick thought out by Preston Price as a way to exact his revenge for his humiliating defeat at the trials, his parents drive them and Tyco to the finals.
After Preston and his dog, Jacques have finished their routine and score a 98, he is shocked and surprised to find Calvin and Tyco back just in time before their disqualifications. He even tells them that it will be impossible for them to beat his score but Calvin refuses to listen and continues anyway. Seeing as to how incredibly well Tyco and Calvin are performing with the whole skateboard-pulling routine through the dog obstacle courses, Emily, Figg, and Calvin's parents are seen cheering for them and Preston, worried that Calvin will win and refusing to admit defeat, takes his dog and decides to take matters into his own hands by sabotaging one of the dog obstacle courses during the show. Nevertheless, Calvin and Tyco still win, beat Preston's score by one point, and get a 99/100, and Preston gets disqualified for the sabotaging.
Along with using that reward money to buy the last comic book, Calvin uses the money for good. He gives the money to the shelter (where Tyco used to be) so that the dogs can have better homes; much to his parents' happiness. In the end, the shelter is saved and Figg along with many other people adopt a new pet. When Figg adopts a Chihuahua named Rufus and seeing how well he is performing with him, Calvin's parents watch as Calvin tries to talk Figg into teaming up with their dogs as a tag team with him as the manager "to help count all the money" for next year's competition. Tyco is made a hero for having saved the shelter after that.