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

[noob]

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.

Why would a weird name make an entire game fall?
In real life there is people with names that are more or less jokes or are extremely awful (like Tristan which means sad)
The more grimdark a setting is the more the people are crazy on average so it does makes sense to decide to call yourself with a weird name and being insane in a grimdark setting.
In the medieval era people often were called in function of what they did (ex: smith) so being called lances a lot would make sense if you were the kind of people who hits other people and kill them with a lance very often. (and being a sir is a title coming from nobility which is also correlated with violence)
lancelot might be named this way because of their use of a lance as far as I know.
So ironically it makes infinitely more sense than someone calling themselves "Auron Darkmoon" while it is rarely considered weird to pick nonsensical names like this one.

Not seeing any "weird names" / names based on what the individual do would be what is odd if we place ourselves in a grimdark medieval setting where most people going adventuring are probably delusional.
Delusional people are the majority if we pick people who go adventuring in a grimdark medieval setting because you need to convince yourself you are much greater and stronger than what you actually are or you just decide it is not worth the risk to your lives.