The premise: Zim (Richard Steven Horvitz) is an incompetent alien warrior sent, as punishment, to scout out the inconsequential backwater of Earth. Since he is a child, he enrolls in elementary school, where the outcast human boy Dib (Andy Berman) suspects his secret.
One would suspect that the two antagonists would eventually learn to trust and support each other, but in fact that never happens. Zim never waivers in his bombastic "We will enslave you all!" contempt of humans. He forms alliances with Dib only when it is essential for his purposes, and then quickly and easily betrays him. And Dib never grows to like or respect the alien; in fact, he takes great pains to torment him.
Thus, no gay subtexts between the two. No beefcake. No nothing.
In the top picture, a fully-nude Dib opens his bedroom door to display Zib sleeping peacefully after a night of passion. It originally featured a very nice full frontal shot.
Here they just hug.
I'm not sure why, but antagonists always inspire much more gay fan art than buddies.
(Original pictures from the artists on deviantart.com.)
See also: Gay Fan Art #1: Max Goof.; and Gay Fan Art #3: Beast Boy