A Guest Fighter is a character that doesn't belong in the setting who just shows up in a Video Game, especially a Fighting Game. It seems like if a Fighting Game hasn't had a Crossover, it has had a Guest Fighter. The name comes from the Super Smash Bros Brawl website, in which the name is used to refer to Solid Snake and Sonic the Hedgehog, the two characters that are outside Nintendo's ownership. In nearly all cases, those characters are The Unexpected, so Guest Fighter can be considered a subtrope of that. Examples of Guest Fighter include: