Okay, these two cover theme games were not guessed last time, so here's another chance, now with CLUES!
Also, people guessed the general theme for #1, but I actually had a crazy specific theme for this one, so I'll leave it, too!
M. Bloom guessed that "These covers all feature characters who aren't who they seem to be," which is true, but there's something more than just that!
HINT: The keys to this cover theme are events that took place after each of the three characters above were introduced.
HINT: This one is very simple, but also extremely EXTREMELY obscure.