It's worth noting that there's a difference between gender-swapped costumes and crossplay costumes. Gender-swapping means changing the character's look to fit another gender, whereas crossplay involves trying to look as though you are the gender of a character of the opposite sex. We'll be featuring a few from both classifications, as well as a few that fit somewhere in between.
1Princess Leia: Star Wars
It takes balls to go as a gender-swapped version of one of the most famous female sci-fi characters of all time, but a quick look at those pants shows that this guy has the goods to become Prince Leia.
2Joker and Harley Quinn: Batman: Arkham City
Plenty of couples go to the convention as the Joker and Harley, but seeing a gender-swapped couple that has accurately captured the distinct character styles from the Batman: Arkham City game—now that's impressive.
3Harley Quinns: Suicide Squad
Perhaps the most popular costume throughout the convention was that of Harley Quinn from the new Suicide Squad movie. While there were plenty of gals dressed as Harley, these two were some of the only men who took on the look.
This year marked the iconic character's 75th anniversary and a panel celebrating that milestone brought out costumed fans of both genders, including this heroic gent.
5Captain America's Hydra Costume
6Jessie: Toy Story 2
Here's a perfect example of crossplay. This cosplayer is, of course, a man, but he didn't change a single detail of the costume to make it more masculine. The result is a spot-on cosplay of the original character which just happens to be worn by a person of the opposite gender.
7Marty McFly: Back to the Future
Another perfect crossplay. This girl makes a fantastic Michael J. Fox cosplayer, and her pose made it all the better.
8Sonic: Sonic the Hedgehog
This Sonic shows that with the right assets, even a super-fast, blue hedgehog can still be surprisingly sexy.
9The Staypuft Marshmallow Man: Ghostbusters
The Staypuft Marshmallow Man may have been one of the all time cutest villains of cinema, and this female version is even more so.
10Sailor Saturn and Sailor Pluto: Sailor Moon
Sure, the cartoon might feature an all-female band of heroes, but boys can love Sailor Moon too. And these two make great Sailor Scouts, even without short skirts.
11Shredder: Teenage Mutant Ninja Turtles
This Shredder may be a female, but I strongly recommend you don't tell her she hits like a girl unless you want to find out why she's always got those turtles running scared.
12Mojiretsu Korigashi: Shimmer Sensation Pretty Cure!
Admittedly, this is a pretty obscure character from a pretty unknown show, but when you see a large mustached man dressed as an adorable little girl, it's hard not to admire the cosplay even if you don't recognize it.
13Louise: Bob's Burgers
Louise is a bit of a tomboy. This fun cosplay takes things a step further, and gives her a glorious beard to go with her iconic green dress and bunny ears.
14Tina: Bob's Burgers
Tina may be a bit awkward in the cartoon but she's got nothing on this cosplayer.
15Engineer: Team Fortress 2
To non-gamers, the origin of this gender-swapped costume might not be immediately obvious, and you'll be forgiven if you thought she was trying to be Bob the Builder or Fix-It Felix from Wreck-It Ralph. The Mann Co. sticker on the front of her pouch makes it obvious that she's on Team Fortress.
16Marvin the Martian: Looney Tunes
Sometimes a great gender-swapped costume doesn't mean just creating a costume that looks like the character changed sexes, but actually turning the character into an outfit for the opposite gender. This adorable Marvin the Martian shows that a little creative sewing can go a long way.