Harry is raising a child (don't care whether it's a canon child or an OC). On the first day of school, he and/or whoever he's sharing parenting duties with (if he is) gets called in because, well, the kid's been around Bob his/her whole life, and Bob hasn't really censored himself...

Heh. Or really awkward early explanations of what Bob's talking about. You know the kind, where they're censored so much that they sound like words describing things the kid sees/does, so they use the words in COMPLETELY the wrong context.