Caillou and Rosie are playing with toys. Mommy comes in and tells them it's time to clean up; however, Caillou purposely blocks her out. Mommy repeats telling Caillou to clean up sternly, and Caillou replies that Rosie isn't cleaning. Momny sighs and tells Rosie to help too. She shows Rosie how to put toys in a plastic bin, but when she isn't looking Rosie runs off.
Caillou is angrily tidying up his toys, when he notices Rosie playing with a pull-toy. Caillou is jealous that he has to clean while Rosie plays. Mommy tries to console him, saying that Rosie is too little to clean up, and that she'll do her share for her, but Caillou pulls away, and Mommy gets mad. Caillou thinks Mommy is being unfair, until he gets an idea.
After Mommy helps with cleanup time, Caillou decides to act like a baby. At lunch, he sees Rosie drinking from a training cup and asks for his milk in a baby cup too. Mommy is very confused by this, but fixes a sippy cup of milk for Caillou anyway. After a long sip from his cup of milk, he declares he wants his sandwich in small pieces "like Rosie," puzzling Mommy even more.
For dessert, they have chocolate pudding. Caillou says he wants a bib. After Mommy puts a bib over him, they eat. In the time a drop of pudding lands on Rosie's bib, Caillou gets pudding all over his face and clothes! He thinks being a baby is much better than being four! Mommy tells him that it's okay if he wants to play baby, but not to be a messy baby. Caillou and Rosie play with one of Rosie's toys together upstairs, and Mommy watches and shakes her head.
Afterward it's naptime. Caillou tries to go to sleep but he can't get to sleep. Caillou decides to be 4 again so Mommy and him play cards while Rosie naps.