"three reasons" meme

With a lack of anything of substance to post, here's another meme. I've seen this one floating around on several blogs in the past week:

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 really fond of. Anyone can tell you reasons not to date Cthulhu, after all.