You never can tell who's behind the mask. Celebs love to play dress up at conventions, going incognito to walk the floor alongside The Rest Of Us. Mark Ruffalo is The Hulk in Marvel's "The Avengers," and Jared Leto is The Joker in DC's upcoming "Suicide Squad," but they both went for very different costumes while trolling fans at New York Comic Con.

Jared even shared a photo with someone dressed as his own Joker (see above) noting that the guy had no idea who he was standing next to. That's just cruel! (And very Joker.) Here are more stealth pics from Ruffalo and Leto, who obviously should've walked the floor together:

#NYCC they had no idea :)

A photo posted by JARED LETO (@jaredleto) on

Had a great time at #comiccon2015 NYC! Thanks ComicCon for the Hospitality.

A photo posted by Mark Ruffalo (@markruffalo) on

Got to hide out and enjoy #comiccon2015

A photo posted by Mark Ruffalo (@markruffalo) on

So sneaky. According to BuzzFeed, Jared Leto also documented his experience on Snapchat, including hanging out with a Harley Quinn cosplayer. Genius. Evil genius.

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