As far as I can tell, there are two major categories of No Heterosexual Explanation Moments. The first is where the plot only makes sense if the pairing is, in fact, a pairing; I tend to put the first season of Smallville (what I know of it) into this category. Lex's behavior is just, you know, really really hard to explain unless he is very hot for Clark indeed. And the second kind is where it's just not something people with a strictly platonic, UST-free relationship ever do. Like, for example, when one cop signs "I love you" to the other cop as he's being med-evac'd out on a helicopter. I am pretty sure they don't teach that in police academy courses on Effective Partnerships in the Law Enforcement Profession, is all I'm saying.
But Frost and I realized that, tragically, we just do not have the depth and breadth of experience to make a complete catalogue of No Heterosexual Explanation Moments. This is where I am hoping you all come in. What are the key NHEMs of our time? Of past times? Of all time? Educate me! Bonus points for links to clips, if they come from a visual medium.
F/F as welcome as M/M, of course. And, hey, if you've got any NHEMs for threesomes, lay 'em on me. The only key is that even a person struggling not to see the pairing will still say, "...You know, I just really think they're doing it." (Obviously, if it is an actual canon pairing, it cannot feature in an NHEM, because in that case there shouldn't BE a heterosexual explanation.)
ETA: Spoilers in comments, of course! And the more the merrier, in my opinion.
Also posted at Dreamwidth, where there are comments.