In today's review of DC Direct's Showcase Superman, yo mentioned the classic essay "Man of Steel, Woman of Kleenex." Written in 1969 by famed sci-fi author Larry Niven, the article posits the problems that Clark Kent would face when trying to copulate with a human woman. That may be a common topic of discussion among nerds today (thanks, Kevin Smith), but it was fresh and creative back in the day.
Anyway, in 1994, Penthouse Comix reprinted the essay, and hired Curt Swan to provide illustrations for it. Completely NSFW illustrations. If you've ever wanted to see a joyfully sky-clad Lois Lane squirming beneath your greatest hero (as drawn by the definitive artist of his generation), well, this is your lucky day!