San Diego Comic-Con has all the trailers, news and merch that a fan of pop culture could ever love, but everyone knows the highlight of the biggest entertainment convention in the universe is the plethora of cosplay. You can't walk three feet without bumping into a few amateur Jon Snows or Deadpools, and it's awesome.

It's also a place to bump into celebrities as they're there to take in the fun and promote their shows and movies. True story: I rode in an elevator with Dennis Miller there once! (Not impressed?)

But sometimes both of those worlds collide in the best way, and celebrities show up in cosplay because they're fans themselves. This year, the highlight has to be Torchwood's John Barrowman dressing up in a glitzy Captain America outfit, but celebs have been going to the con in their favorite costumes for years. Take a look at the gallery we've collected below and see for yourself.