Obviously some people here use pseudonyms and some don't.

Pseudonyms or monikers used here are created by the individuals who use them so it is free-will at work. It sounds like you're looking for pithy ways to get away with name-calling, like if it's clever enough maybe it will stick.

George W. Bush had a habit of giving people silly nicknames. Because he spoke them they tended to stick or be referenced in future mentions of the individuals in question. I can't imagine that they're all happy about that.

I think this must be something more popular across the pond.

SRS