The episode begins with Caillou and a pregnant Mommy in the backyard. Caillou asks if she (the baby) is coming today and Mommy says she is going to go to the hospital later that day, and that his grandmother will look after him. Caillou's Mommy and Caillou's Daddy leave for the hospital and Grandma comes to watch Caillou. Caillou can't wait to meet Rosie for the first time. Soon, the car appears in the driveway and Caillou excitedly runs for the door. Mommy shows Caillou his brand-new baby sister, Rosie, but before Caillou can get a good look, Grandma runs over to see the new baby, saying "Oh, she's just beautiful! She's absolutely adorable!" Mommy, Daddy, and Grandma reply with "Isn't she gorgeous?", "She's my special girl!", and loud wailing, respectively.
Caillou is angry and jealous that no one is paying attention to him, thinking they only care about Rosie now. He goes to his room, sits on his bed, and then throws his ragdoll onto the floor in anger, wanting nothing to do with it anymore.
Later, a hurt Caillou trudges sadly into the nursery where Caillou's Daddy and Rosie are in a rocking chair. When Caillou is asked if he'd like to rock the baby, he responds with a huge "NO!" Daddy gets up and sets Rosie on a changing table so he can get some diapers from the linen closet. Meanwhile, Caillou scoots a chair over to the changing table and climbs onto it. Caillou grabs Rosie and kisses her, and for a second it looks like he is making up with her...until he suddenly grabs Rosie's cheek.
Daddy hears the loud shrieks and sees Caillou holding Rosie down, his hand still on Rosie's cheek. He scoops up the bawling infant and cradles it until it stops crying.
Caillou's Daddy asked why he did that. Caillou told him he didn't like Rosie because she didn't play with him. Caillou's Daddy tells Caillou that Rosie is too little to play, and tells him about the good things about being a big brother and Caillou helps change Rosie's diaper and he began to like Rosie more, he even got to hold her!
- This is the only episode that took place when Caillou was 2 ½.
- Gilbert is seen this episode, so Caillou's family has had him before Rosie had been born, but in the episode New member of the family when Gilbert becomes Caillou's pet after Rosie has already been born.
- Caillou pinching Rosie's cheek, however, is less harmful than what he does in the original book, where he bites Rosie.
- At the beginning of the episode, Caillou talks like a 2-year-old. After he pinches Rosie, he speaks in complete sentences like he usually does.
- It is possible that a few months passed between Rosie coming home and Caillou being jealous, and Caillou pinching Rosie.
- If you look at Mommy when she shows Caillou his sister and says "this is Rosie," you can see that her mouth doesn't move.
- On the cover of the book that the Grandma shows with Mommy holding Rosie, you can see she still looks like she is pregnant.
- Caillou wears a yellow shirt and red overalls in this episode.