When Garfield torments Nermal, an old TV host gives Garfield a lesson in treating Nermal better by taking away his colors.
Garfield watches a mystery show about who stole the jewelry. Just as the inspector is about to determine the culprit, the TV breaks much to Garfield's dismay. He then blows the "TV is broken" alarm which informs Jon of the situation. Jon sends the TV to be repaired and replaces it with an old black-and-white television previously owned by his grandmother. Garfield decides to try it and watches a puppet show starring Dr. Goody-Good, only to be interrupted by Nermal. Nermal asks Garfield to help him direct a movie about himself, only for Garfield throw him out of the house and onto a garbage can as a "spontaneous live-action start".
As he returns to continue the show, Garfield is surprised when he finds out that Dr. Goody Good can actually see him and hear him outside the TV box (something which Jon was told about by his grandmother when he was a child). Dr. Goody Good scolds Garfield for the way he mistreated Nermal, despite Garfield trying to convince him how Nermal is a bad cat, and strips Garfield of his colors as punishment; thus rendering him completely grey. Dr. Goody Good says he will only return Garfield his colors if he does three good deeds, so Garfield wanders around the city doing good deeds to people. He helps an elderly woman cross the street and saves a fat man who is eating ice cream from a nearby falling piano (albeit the second one only got Garfield injured since he was the one to be crushed by the piano).
As he recovers, Garfield sees that most of his colors have returned with his head being the only remaining grey part left. Seeing as he still has one good deed to do, Garfield climbs up a building to search for more people that need help. He then spots a nearby ally where he witnesses Nermal being attacked by wild stray dogs. Though initially reluctant due to his dislike for Nermal, Garfield decides to save him anyway feeling that "a good deed is a good deed, even if it's for Nermal". Unfortunately, his intervention only made the dogs attack him instead of Nermal. After the dogs viscously beat him up, Garfield finds that his head has also regained its natural color. Nermal is not appreciative, and remarks how stupid Garfield's actions were.
Garfield excitedly runs back to his house to thank Dr. Goody Good. When he arrives, he sees the real TV fixed and being watched by Jon and Odie. Jon tells Garfield that his grandmother's TV is being taken away by the repairmen and Garfield tries in vain to catch up to their truck to speak to Dr. Goody Good. He sadly returns home and Jon shows him that the puppeteer of Dr. Goody Good is long retired as confirmed when he looked him up on his computer. As the trio leave the room, Garfield thanks Dr. Goody Good for teaching him a lesson about sharing. Unbeknownst to Garfield, the image of Dr. Goody Good on the computer replies saying Garfield did well.