Say that I write a computer game that involves a number of characters. I choose to trademark some of the characters I think are more marketable, and copyright my game. To my surprise, fans discover that it is possible to glitch the game in such a way that a new character is created (perhaps it's a Frankenstein-type character of other parts). It rises in popularity and becomes fairly recognizable.
Does the fact that it was an unintentional creation still mean it is eligible for trademark or copyright protection?
For reference, this sort of thing happened in Pokémon Red Version and Pokémon Blue Version. It is possible to glitch the game to create what appears to be a Pokémon called "MissingNo.", which was clearly unintentional. It became pretty popular and is rather recognizable among those who played the games. To have a more specific version of the question, could Nintendo theoretically choose to trademark "MissingNo."? Is it protected under copyright?