The episode begins at the Jötunheim residence, with Gumball and Darwin being assisted by Hector to build a diorama project of The Barrier Reef. He successfully inserts the paper octopus there, much to Gumball and Darwin's satisfactions. However, Hector accidentally blows the project far away, where it flew into and knocked out Goblin, who was taunting to a protesting Mr. Small that nature can't fight back against him. Hector then complains to Gumball and Darwin that it's not great to be huge, for various inconvenient reasons. Gumball then comes up with the idea to use one of Mrs. Jötunheim's potions to shrink Hector, although Hector tells them that his mother won't allow it. Darwin, meanwhile, continually misunderstands Gumball's plans, much to his frustration. Mrs. Jötunheim then says to the two that she won't allow for a shrinking potion to be used on Hector, because he should learn to accept himself for who he is. Gumball tries to argue with her but realizes that there's no point in trying to argue, so he politely decides to leave the situation. When Gumball and Darwin exit, Gumball reveals that he stole Mrs. Jötunheim's potion book.
Gumball and Darwin make a shrinking potion in their house, and decide to test it on a bee, although they accidentally drop the sample potion and drop it on Larry's car, causing the car to shrink but not Larry, and Gumball and Darwin are eager about the results.
The two then persuade Hector to drink the potion, who's tempted in drinking it, although he reminds them that his mother won't approve of it. Eventually, Hector decides to drink the shrinking potion, and it immediately shrinks him down to around the size of the two without any dramatic shrinking effects. At first, Hector's extremely eager to be small, due to being able to use his full volume and being able to wander around freely. However, whenever he tries to enjoy everyday life, he either becomes exhausted or pushed around by others. Hector becomes depressed at being "like everyone else" to the point where he decides to sit on a swing, although he has to get off it to share the swing with other depressed people.
Hector then tells Gumball and Darwin to he wants to be to being a giant again, and he rudely says that he doesn't like living with other people with his current size. As a result, he demands to the two that he return back to his giant size.
Back at home, Gumball and Darwin are making the potion that will turn an impatient Hector back to normal. Hector drinks the potion, but Gumball realizes that Darwin mistook "Orangutan toenails" for "0 rangutan toenails", meaning that he didn't put any orangutan toenails for the potion recipe. They notice that Hector develops mutated results (still the size for Gumball and Darwin) as a result, and the potion continually mutates Hector into weird features. Darwin tries to call Hector's mother for help, but Gumball tries to prevent Darwin from doing so, fearing that they'll be in trouble in the process of doing so, while Hector continues to shape-shift. Gumball comes up the idea of sneaking through Hector's cave to obtain orangutan toenails.
Gumball and Darwin try drag a now insane Hector near his cave, and they sneak through Mrs. Jötunheim to obtain orangutan toenails. When Hector starts shapeshifting again, he shrinks down and falls into a spider cobweb, and Gumball and Darwin become shocked by it approaching Hector. However, it turns out that the spider wanted a hug from Hector, and Gumball realizes that Mrs. Jötunheim is using orangutan toenails to brew her potion. Darwin accidentally lights up a tiny Hector from the magnifying glass, and although he then extinguishes the fire, he accidentally swallows Hector, who shape-shifts to a larger size, making Darwin choke. Gumball eventually eventually manages to stealthily obtain the jar of orangutan toenails, and he feeds it to Hector, who increases back to his usual giant size. Mrs. Jötunheim tells Gumball and Darwin to come over to see her drinks and a baked cake, which says, "I know what you did you boneheads." She reveals that Darwin didn't hang up his phone the whole time when he called her. Gumball then questions her whether the drink she gave Gumball was actually a potion, and she reveals that it's a short term one that turns their hands into butts, ending the episode.
Hector previously dreamed of being the size of other people in "The Night," and his dream came true in this episode. However, Hector ends up becoming depressed as a result of being regular sized, due to various struggles as one.
Hector stating that he swallowed the last girl he kissed is a reference to "The Shippening," in which he tried to kiss Masami but instead swallowed her.
When Gumball said to Hector that when he becomes shrunken down, he can have his mother blame rap music for shrinking him, he references how rap music tends to start with "lil" in their songs.
The cloak that Gumball and Darwin used to become invisible is a reference to the Cloak of Invisibility from the Harry Potter series.