A Norwegian children's book from 1949 about tooth trolls who inhabit a kid's mouth. The problem? The kid, Jen, always forgets to brush his teeth, so the trolls Karius and Baktus flourish at his expense.
Tropes:
- Color-Coded Characters: Karius and Baktus are near-identical tooth trolls. We can only differentiate them because they are, respectively, black-haired and red-haired. In Karius' case, as his name references cavities, it's relevant because rotten teeth blacken.
- A Lizard Named "Liz": Karius and Baktus' names respectively draw from Caries (cavities) and Bacteria, with the former being the primary cause of the latter.
- Talking Pest: The title characters live the easy life in the mouth of a boy who never brushes his teeth. It's widely used to teach children about the importance of brushing their teeth. Depending on the adaptation and the age of the audience, it can Scare 'Em Straight.
