Has Another Player’s PC “ruined” the Tone of a Game for you?

[Trask]

Had an entire game fall through because a guy reeeaaally wanted to make a Halfling Cavalier named "Sir Lances-a-lot" once. Nobody else was into it and he would not budge on the matter.

It is supremely irritating to me when a player just absolutely MUST play this one idea they had, regardless of how poorly it fits or any other circumstances, even if the idea isn't a joke (although it usually is) the total refusal to make concessions is a red flag to me.