sketchball

A weird guy who is socially inept, makes off-color remarks, does strange socially unacceptable things, and has strange interests.

This is the guy at a party who talks to you and scares you, not intentionally, but he doesn't know any better, and you want to leave real quick.

Q. Did you see that guy dancing to Duran Duran by himself in the workshop? A. Yeah, what a sketchball.