Appearing once or several times, minor characters are the ones who don't get to say much. Or, perhaps, appear as a pivotal role for a single story.
“Plutonium Blonde is a former superhero and member of the Superdead. Plutonium Blonde was born in...Plutonium Blonde
“Minor in his roles, Big Iron is a generic black cape trying to blow things up for money. Big...Big Iron