I can't tell if they are going to the prom or to go LARPing. That's LIVE ACTION ROLE PLAYING. People get together and dress up as warriors, mages, or whatever other things there are in the fantasy world, and then they beat each other with foam swords. It sounds completely awesome, but I'm also terrified to get into it. I might never emerge back into the real world. I'd be all about that LARP life.
These two are certainly a match made in heaven. Imagine how much fun they must have had building those costumes together. That's a huge part of the fun of making your own prom outfits. It looks like these are made out of duct tape, so it's possible that this was part of the duct tape prom outfit craze. These are some of the coolest duct tape outfits I've ever seen.