I recall that as a kid I saw the same game with two titles: Ghosts 'n' Goblins, and Ghouls 'n' Ghosts. There may have been others (anyone?)
I'd like to know why there were different names for the same title. Was it a copyright issue as we say in Europe for StarFox / Lylat Wars? Possibly the same case for Contra / Probotector (unless it was a name change to go with the robots as Germany did not like humans killing humans hence the character change).