In the name of "enhappying" the bride (and groom) their friends dress up/ do foolish things, usually inside joke related. This also serves the purpose of letting the bride and groom sit down in between sessions of dancing, which are usually pretty athletic. Especially considering that the bride and groom have been fasting until about 5 minutes before dancing starts.
At any rate, I've seen some bizarre things, including guys dressed up as food (I think Aqua Teen Hunger Force, but the costumes were pretty bad, so: unclear), girls carrying those molecular models you get in chemistry class (the bride is a chem PhD), and a bridesmaid that looked like a matador. Oh wait, her dress was just unfortunate, it wasn't part of the "bull and bullfighter" dance that is prevalent, and incongruous (you know, the one where one person waves a napkin, and the other runs towards it with fingers on their head like horns?).
This video has an example of the bullfighter about 10 seconds in.
Instead of dancing, you could wave flaming nunchucks, like this guy. Also, if you look at the comments below, I like how one of the commenters seems to believe that flaming nunchucks are traditional at a Jewish wedding, saying "I wanna go to an Orthodox wedding, so fun." To which someone responded: "yeah they r fun, at my sisters wedding some guys put their black hats on fire (old ones ofcourse) and they juggles fire and knives 2." Really? Flaming hats? Clearly I'm attending the wrong type of weddings.
Now, like many Jewish traditions, this one has been co-opted by the guys. What seems pretty clearly to be a mitvah for the benefit of the bride is often in practice a bunch of guys doing silly things, often an inside joke with the groom.
Like these guys with their "Riverdance." Not that it isn't funny, but after googling "Wedding Shtick" I only came up with male entries. This could be, in part, because shtick often involves singing and/or dancing, which can be religiously problematic if done by women (in front of men).
More guys dancing.
For my own (hypothetical) personal wedding, I expect the girls to bring the game. For serious yo. I'm talking to you, roommate. And my wedding can totally be an "arts and crafts project."