Superman: 20 Easter Eggs You Probably Missed
5. Martian Manhunter
After imprisoning Superman in a pocket universe, Lex refers to him as a "Martian," only for Superman to correct him that he's not a Martian, not being from Mars and all.
This being a James Gunn joint, it's impossible to view this as anything but a nod to the fan favourite DC character Martian Manhunter - a green-skinned humanoid from Mars who is also one of the inaugural members of the Justice League.
Though we don't see the character in this movie, it seems like it's just a matter of time before Gunn introduces him in a future DC film, considering how perfectly suited he is for the filmmaker's sensibilities.
It's also worth noting that the White Martian-esque creature who ferries Supes through the pocket dimension is not of that species, but was instead created by Lex at some point before the events of the film.