Fans had no idea they were posing for photos with their movie heroes, as the stars were completely unrecognisable behind baboon and ugly old man masks.

Leto, who plays The Joker in the much-anticipated Suicide Squad movie, aped around at the convention, thrilling fans who asked to take his picture, while Avengers star Ruffalo ditched his The Hulk disguise and hit the event dressed as a cigar-puffing old man.

Both stars posted photos of themselves in disguise on social media. Ruffalo shared pictures of himself in 'costume' on Instagram, writing, "Got to hide out and enjoy #comiccon2015."