Caillou is a French-Canadian educational children's television series, based on the books by Hélène Desputeaux. It centers on a 4-year-old boy named Caillou who is fascinated by the world around him.
When Lois tries to find the reason behind Stewie's new gift of cursing in "Stewie's First Word", she blames Caillou and sits out to watch every single episode to find proof of it. As part of an episode is shown where Caillou thinks he's a cancer patient because he's bald, Lois ends up falling asleep and later calls the episodes dull, but finds no evidence of cursing. The narrator also mentions how Caillou's low testosterone dad is spoiling Caillou in every episode, claiming that he wants to raise his son to be a psycho. In the vocals, his dad tells him that they're sitting on the washing machine because in Canada, men have vaginas.
When she later tries to set a trap for Peter by polishing the stairs so that he'll fall down and curse, he trips but does not utter a swear as he falls down. When Lois inquires about where he learned to be polite, he attributes it to hanging out with Caillou's 'beta dad', named Boris in the show.
The narrator torments Lois outside of the Stop 'N Shop when she needs to use the bathroom real bad and the employees lock her out.
To prepare for his 'mommy and me' date with Lois in "Mister Act", Stewie decides to get waxed and requests for it to look like Caillou.
Caillou is voiced by Henry Holcomb.