It is Halloween and Caillou is very excited. Caillou's Mommy says that it is time to go trick-or-treating. Caillou gets his astronaut costume on. Rosie said she wanted to be a clown but when she saw her costume she didn't want to go so Caillou's Mommy stayed home with her while Caillou's Daddy took Caillou trick-or-treating. They go to Mr. Hinkle's house first, Mr.Hinkle likes Caillou's costume and gives Caillou candy and some to give to Rosie. Caillou goes to some other houses and then meets up with Leo who is frankenstein's monster and Clementine who is a dressed up as a nurse. They go to a bunch more houses and get a lot of candy. They then go to one last house, Caillou's house, Rosie is scared but she takes her brother's helmet off then realizes that Caillou is home and he, Leo and Clementine go inside and munch on candy.
- This is the first Halloween special in the Caillou franchise.
- In "Caillou is a clown", Rosie overcomes her fear of clowns but in this episode she is still afraid of them. This episode took place before "Caillou's a clown."