Tell me which of these are main characters from The X-Files: Fox Mulder, Mitch Pileggi, Dana Scully, Mully & Sculder, Frank Black, Peter Watts.

Fox Mulder and Dana Scully are characters from Chris Carter's show The X-Files. Mitch Pileggi played Assistant Director Walter skinner on The X-Files, Mully & Sculder is the name of a synth-pop duo from Canada, and Frank Black and Peter Watts are characters from Chris Carter's other sci-fi show called Millennium. Frank Black made a cameo on The X-Files after Millennium was canceled, but is not considered a main character on the former.