Grew up in New Lisbon, Wisconsin. Studied art at the University of Wisconsin. Created the strip "The Student Norm". His friendly rival from another college at the time was Mark Gruenwald. After college while in New York, he showed off his works but he wasn't so lucky. Both DC Comics and Marvel weren't interested. Dennis gave it a second shot by submitting cover artwork to DC Comics. This time things turned out better, and he was offered an inker's position at DC Comics by Joe Orlando.