Calvin comes home and tells Mom he got a part in the class play. He gets to say a line. Mom tells him that's wonderful. Calvin believes this is a great dramatic role, and he'll have people in tears by the second act. The play is "Nutrition and the Four Food Groups". Calvin will be an onion.

Calvin asks Hobbes to help him learn his line for the play. Calvin reads the line, gives the script to Hobbes, and Hobbes tells him to start. Suddenly, Calvin realizes he's not in character yet. He doesn't have his motivation. Hobbes wonders if it's fame. He supposes this role could be a big break.

They're still rehearsing. Hobbes reads the line before Calvin. Calvin starts his line, and stops. He starts again, and stops. Suddenly, he falls to his knees, says he hates the play and bemoans his inability to learn the part. Hobbes suggests his emoting is down pat.

Calvin has it figured out. He tells Hobbes the play is no sweat. Hobbes asks if Calvin has his line memorized. Calvin replies that he doesn't. He figures he'll come on stage, do a little soft-shoe and ad-lib something. Hobbes wonders how he'll ad-lib something on dietary fiber. Calvin thinks he could also do his onion in mime.

Calvin asks Mom how his onion costume is coming. Mom is still working on it, and she wishes the class would do something less elaborate. Calvin says to be glad he's not Russy White, who has to be an amino acid. Calvin puts the costume on. He thinks it's "Jabba the Hutt meets Rudolf the Reindeer".

Calvin wants to know if Dad is coming to the play. Dad says he'll probably be at work. Calvin tells him it will be great drama. Dad asks Calvin to read his line now. Calvin starts, then forgets. He starts again, then forgets. Dad figures with 25 kids in food suits forgetting their lines, he'll definitely be at work.

Susie asks Calvin if he has his line memorized for the play. Calvin says he's still learning it. Being an onion is a difficult role. He asks Susie what she is. She replies "Fat". Calvin says "No. I mean in the play". She smacks him and asks whether anyone else wants to say it. Calvin lies in a heap on the sidewalk calling for his understudy.

Calvin is waiting in his onion suit at the bus stop. Calvin tells Hobbes he feels like an idiot. He says he'll be glad when the play is over. Hobbes yells for Calvin to run for his life, a produce truck is coming. As Calvin runs off, Hobbes yells that he was just kidding.

Miss Wormwood asks Susie where Calvin is. Susie says she doesn't know, that he was just there a minute ago. She wonders if he went to the bathroom. Miss Wormwood says he's on stage in two minutes. He picked a fine time to go to the bathroom. Calvin, in the bathroom, says it's a fine time to get stuck in his costume zipper.

Calvin can't believe he's stuck in his costume zipper. He figures he can't go on stage with his shirt caught in his costume. He knows he should be onstage reciting his line. He wonders what to do. From the bathroom, he shouts out his line.

Calvin comes home, and Mom asks how the play went. Calvin tells her he got stuck in his zipper, they had to stop the play, and the janitor had to find him and get him out. Mom says that was terrible. Calvin says the play was ruined, but he remembered his line.