Complex sentence: An avid science fiction fan, Cole was known for slipping in sci-fi elements even when they weren't appropriate, such as rocket ships and ray guns appearing on the covers of Captain Flight Comics "and" Contact Comics.
Split into simpler sentences: An avid science fiction fan, Cole was known for slipping in sci-fi elements even when they weren't appropriate. Cited examples are rocket ships and ray guns appearing on the covers of Captain Flight Comics "and" Contact Comics.