Joe has a broken leg

Joe has a broken leg.
His friend Mike comes over to his house. Joe says:
– Do you mind getting my slippers?
Mike goes upstairs and see’s Joe’s hot 18 year old twin sisters. Mike tells them that:
– Joe sent me up here have sex with both of you.
One of them says:
– Prove it.
Mike shouts downstairs and says:
– Both of them?
Joe yells back and says:
– What’s the point of fuckin’one?