T-Rex: Many amazing characters are still under copyright: Batman! The Joker! Poison Ivy!
T-Rex: Other non-Batman characters, probably!!
T-Rex: However, there is a loophole in copyright, which is that it's TEMPORALLY WEAK. Anyone with a time machine could simply travel AHEAD in time to when they can sell "Batman meets Ivy And Joker Is There Too" stories till their heart's content, or go BACK in time and write said stories for a Renaissance audience!!
Utahraptor: You're right! Copyright IS vulnerable to exploitation by those with time machines.
T-Rex: Yesssss
Utahraptor: But so too is everything else, including REALITY ITSELF, so it's not THAT big a loophole. Heck, with a time machine you could travel through time and MEET Batman, so your little stories aren't a huge concern.
T-Rex: Wait, what?
Off panel: There's gotta be someone across ALL TIME who's absolutely the most like Batman, right? So just find him and meet him.
T-Rex: DUDE, this is NUCLEAR-GRADE motivation to become a scientist!! Oh man! I gotta go!
T-Rex: I gotta study, like... physics??