1. Daria and Jane
2. Hillary Clinton and Sarah Palin
Dream team, amirite? Hillary gets to wear a PANTSUIT, and Sarah gets to have an annoying accent!
3. Betty and Veronica
4. Ann Coulter and Rachel Maddow
If you don't mind play-hating each other for photo ops, this is a hilarious costume. It would be fun, surprising, and totally weird. No one would see it coming. You both have to perfect a variety of the bitchface, though.
5. Lil' Kim and Missy Elliott
If only, if only. One of you gets to dress entirely in spandex, the other gets to dress entirely in sweats. What could be more perfect? Also, you could definitely do competing performances.