Nightcrawler

Nightcrawler was the superhero alias of Mutant Kurt Wagner.

Biography
At some point, Nightcrawler teamed up with writer and mangaka Jay Eales to fight four Doctor Whos. (PROSE: Contributors)

Behind the scenes
While not specified in PROSE: Contributors, Kurt Wagner, aka Nightcrawler, is a Marvel character from X-Men, specially a German mutant with blue tattooed skin, and with physical features typical of that of a demon.

Apart from the official crossovers between Doctor Who and Marvel, this is one of the only times a Marvel character has unofficially appeared in the DWU.