Caillou began as a series of French Canadian children's books by Christine L'Heureux and illustrator Hélène Desputeaux before becoming an animated television series in 1997. The show followed the everyday adventures of its four year old title character and aired internationally in multiple languages, which is why searches for the intro text and German lyrics remain common. As early viewers grew up online, the theme became a shared nostalgia cue on YouTube and social media, reused both affectionately and as an ironic shorthand for childish innocence.