Continuity mistake: Dave goes to the hospital to visit Night Bitch. He said "I'm Kick Ass", while removing his glasses with his left hand. In his right hand, he has flowers. When he sits on the bed he is instantly wearing his glasses again.
Trivia: When Dave flashes back to his Dad caring for him as a kid, his Dad is putting up a poster for a comic called Superior, which is another comic series created by Mark Millar (creator of Kick Ass), currently in development for a movie as well.