The Bad Romance Meme:
Ganked from petra.
Give me a character's name and I will tell you three reasons why it would be terrible to try to date them, have sex with them, or be in a long-term relationship with them.
For an extra challenge, pick characters you know I'm fond of. Anyone can tell you reasons not to date Cthulhu, after all.
I've definitely done this one before so feel free to be creative and pick characters from newer OR more obscure fandoms.