Larry Laffer:
Robin Williams

I doubt Robin Williams would do this in real-life, but I thought he was just perfect for the part.
Larry Lovage:
Ryan Reynolds

As for the women, there's just really so many possibilites and you haven't been more specific so I'll just throw a bunch of names at you.
The Steryotipical blonde: Huge breasts, ditsy, slutty. Late teens-twenties.
Jaime PressleyA Brunette: Kind, sweet. Girl next door type. Late teens-twenties.
Linda CardelliniA Redhead: Fiery both in personality and in the sack. Late teens-twenties.
Alicia WittThe teacher: Glasses, plays hard to get, but is a maniac in the sack. Very attractive. Thirties.
Elizabeth HurleyThe Band geek: Really geeky. Plays kind of retarded at moments but in the bed, she is very kinky. Late teens-twenties.
Chyler LeighBTW, do we get any payment for this?