Hoping for one last adventure with his old Crimson Chin action figure, Timmy wishes himself doll-sized. Hoping for her first romantic adventure with Timmy, Tootie grabs the doll-sized Wanda and Cosmo, in an attempt to lure Timmy to her. In order to return to normal size, Timmy must rescue Cosmo and Wanda without breaking a little girl's heart.
Timmy, Chester, and A.J. are outside in Timmy's back yard, skeet shooting their old toys with slingshots. Among the toys is Timmy's Crimson Chin doll, last year's model, and Timmy is tired of the doll's lame catch phrases and wants to destroy it. Before they can launch the doll, Timmy hears a little girl calling him. Chester grabs a pair of binoculars and spots Vicky's little sister, Tootie, a nine-year old girl with glasses and a huge crush on Timmy. He and his friends run into their "Anti-Girl Fortress", actually Timmy's tree house, before Tootie can get to them. Before Timmy and his friends arrive, Cosmo and Wanda use their magic to change the tree house into a place resembling the deck of the U.S.S Enterprises from Star Trek. A screen appears with Tootie's image on it, who is calling them asking if she can come up and play.
Timmy orders the "phasers" fired at her, which is actually water balloons, and the balloons soak Tootie who starts crying. Timmy launches another one at her, she attempts to dodge it, but Cosmo and Wanda's magic cause the balloon to hit her anyways. She appears to be driven off, but Timmy and his friends ran out of water balloons. Chester offers to get more balloons so they can strap the Crimson Chin doll to one and throw it at Tootie. Timmy realizes this is the end of the line for his action figure, and starts to feel remorse, so Timmy wishes he and the Chin doll could have one last adventure. Cosmo and Wanda shrink Timmy down to toy size and make the Crimson Chin doll able to talk and move on its own. However, Tootie has come back and is trying to get inside the tree house. The Crimson Chin doll grabs Timmy and brings him to safety. Tootie grabs Cosmo and Wanda, who have poofed themselves into dolls, and wants to add them to her "Timmy love shrine". Cosmo suggests to Tootie, under the guise of an action phrase, that Timmy would come over to her house to get them back. Seeing an opportunity to meet Timmy, Tootie takes the dolls to her house. Returning to the tree house, Timmy realizes that his godparents are missing. The Crimson Chin doll flies off, leaving Timmy alone, doll sized, and at the mercy of his returning friends who cover him with honey and launch him into Mrs. O'Leary's yard, Timmy's beekeeping neighbor. Before Timmy can be stung though, the Crimson Chin doll saves him.
At Vicky's house, Tootie is playing a game with Cosmo and Wanda, imagining herself and Timmy as the dolls and mashing their faces together, forcing them to kiss each other. A game which Cosmo takes much enjoyment in. Tootie reenacts the days' events by soaking "herself" (Wanda) with water, causing Wanda to comment that Timmy should play nicer with Tootie, although Cosmo insists that Wanda is being cleaned. Outside, Vicky is blackmailing two random boys she is babysitting. She forces them to do her chores, or she will show high definition photos of them entering an R-rated movie to their parents. One of the boys begins mowing the lawn while Timmy and his Crimson Chin doll are exploring it, nearly sucking them into the lawn mower in the process before the Crimson Chin destroys it with Chester's retainer that Timmy and his friends had launched earlier. Vicky hears Tootie laughing upstairs with her new toys, and decides to go force her little sister to do her chores. Seeing that Vicky is distracted, Timmy attempts to get inside Vicky's house but is stopped by Doidle, who grabs the Crimson Chin figure in his mouth and runs off into the house!
Tootie places Cosmo and Wanda on a plastic wedding cake and simulates her and Timmy's "marriage" when Vicky comes into her room and takes her new toys. She threatens to introduce them to "Mr. Hammer" and "Mrs. Saw", causing Tootie to cry and say that they are really Timmy's dolls. This only makes Vicky even more inclined to destroy the property using "Mr. Fire". Downstairs, Timmy sees Doidle tearing the Crimson Chin doll apart, and causes a distraction by spilling a glass of lemonade on the floor near Doidle. Vicky hears the crash and goes downstairs to find out what it was, taking Cosmo and Wanda with her after Tootie crashes into a wall trying to fight her. She sees him chewing on a toy and the broken glass in the kitchen, Then she says, "Bad dog! You know you're only supposed to do that outside, or at Timmy's house!". She grabs Doidle and drags him outside. Cosmo and Wanda appear near Timmy and tell him to grab his stupid doll so they can leave, Timmy tells him that the doll is his friend and he should have treated him better. Timmy and his fairies hide in the kitchen when they hear Tootie crying because she thinks Vicky stole Timmy's dolls!
Wanda tells Timmy that the Crimson Chin doll isn't the only one he should treat better. Cosmo said that even though Tootie may be creepy, she has to put up with Vicky more than Timmy. Timmy agrees, and realizes that whenever Vicky is not babysitting him, she's torturing Tootie and it makes her more miserable than Timmy. He goes to apologizes to Tootie. She is happy to see him at first, but angry that he threw water balloons at her. Timmy explains that he is just a dumb ten year old boy, and won't be interested in girls until he is a dumb eleven year old boy. The Crimson Chin doll offers himself to be given to Tootie as a gift, which Timmy calls an "oddly specific action phrase". Tootie is so happy with all this she starts bouncing up and down. However, they hear Vicky approaching, so Timmy runs off. Before he leaves, however, he wishes the Crimson Chin doll indestructible with a 12,000 I-Hate-Vicky catch phrases. Vicky tries to break Tootie's new toy, but is bombarded with insults as her blowtorch is unable to melt the doll. Timmy wishes himself back to the tree house, where he assures himself he will be fine as long as Chester and A.J. never learn he helped a girl. Unfortunately, Tootie has already arrived at Timmy's tree house, showing off the new doll he gave her (only it now wears a pink hat similar to Timmy's) to Chester and A.J. They give Tootie a water balloon and she throws it at Timmy, thinking that is his way of showing love. At the end, Timmy mutters, "Love stinks," to which Cosmo replies to the soaked Timmy, "and it's wet too!" Everyone laughs at Timmy, then his action figure ends the episode by exclaiming, "Brush your cleft EVERYDAY!".