IDEA. IDEA JUST CAME TO ME. Cuz I think this prompt may be best served through similarity recognition. Like, in the middle of a battle against some bad guys, Steve or Tony makes some off-hand comment comparing the situation/the bad guys/some detail about the fight to a similar situation in Lord of the Rings, and the other is all "o.o you like LotR?" and be all surprised and pleased, and then they get to bond over Tolkien while kicking the crap out of bad guys who remind them of orcs or something.

Or ENTS. They should be fighting magically-animated trees in Central Park and compare them to Ents. *flail*

And at some point Tony should set the Ents on FIRE. Ents are hilarious when on fire.

Gah! How can I have such great ideas and yet be unable to write them?