This one takes a while, but is one of my all time favourites.

A guy walks into a bar and sees two beautiful young women sitting very close to each other in a booth. He has a few drinks, notices that they seem to be eyeing him so he goes over and asks if he can join them. They warmly welcome him, have a few more drinks and are getting along wonderfully. The bar closes and he asks if they'd like to go back to his place, to which they say they'd love to. As they get up out of the booth he realizes that they're siamese twins joined at the hip. Undaunted, he takes them back to his house, they have a few more drinks and are getting along royally. He finally invites them to 'Go Upstairs'. They say they'd love to and they all get naked and jump into bed. While he's having intercourse with one, the other is glancing around the room and notices a trombone. "Do you mind if I play your trombone?" she asks. "By all means' he replies. He continues doing his business with the one while the other plays "Tra la la boom de ay" on the trombone. He then switches partners, the one who is no longer occupied looks around the room and asks "are those juggling pins, can I use them"? "Sure" he says. He continues having wonderful sex with her sister as she juggles.

The next day the girls are talking. The one says "I had a great time last night, he was a really good guy. Do you think we should call him?

To which the other says "gee, do you think he'll remember us?"