Wow, that is boring. The martian Manhunter is a shapeshifter like Best-Boy from Teen Titans and yet you mostly find #34 stuff about them doing plain, dull, uninspired sex. If I had shapeshifting powers then I would transform myself into Cthulhu and have sex with 13 women at once! C'mon guys, if I want plain, dull, uninspired sex then I watch the generic shit you found everywhere on the interwebs.
I can't cite my sources, but one explanation I remember was Superman invented special lamp for over his bed that imitated red sun radiation enough to basically reduce him to the level of a normal human man while it was on. Admittedly, probably not a great deal of spontaneity in their lovemaking, and one can only listen to that "Turn on the Red Light" song play so many times before the thrill is gone. :P
@hhhhhhhhyhyhyhy I mean, it is porn. Porn with decent plot is hard to come by. It exists, sure, but I'd estimate that even if you discount works that don't even attempt to have plot, 90% of porn with plot is poorly written. This is why those rare instances of engaging plot in a porn work are so special. The best such cases can even be good enough to distract you from the porn, and engage on the quality of the story alone.
This isn't one of those gems though. It is a work that is more driven by the pairings that it wants to provide porn of than by any real plot that might be added as flavor around that.