Vampires are, traditionally, bisexual in the sense that they seduce both genders in order to suck their blood. I almost think I have heard the slang before, but I can't recall where. And it is odd that there's like zero confirmation of it anywhere online, so I might just be imagining that I heard it.
Its not that they like to suck on things. That's like the juvenile, "Hur hur I made a gay joke" thing. --- Underwater Spartans: http://www.youtube.com/watch?v=GUhjsL2tOkA
Which is of course hilarious, because bisexuality has nothing to do with "sucking on things" - homosexuality does.
Any more backpedaling?
Bisexuality, being emotionally or sexually attracted or involved with both genders.
Sexual activity includes sucking on things.
Male on Male oral sex isn't exclusive to homosexuality kiddo. --- I am a dedicated member of the "Walter Sullivan Is Bad-Ass" group!!! I am the true originator of the Cookie Demon theory on the SH2 and 3 boards.