Blow-up dolls
 

There were these two guys at the pub, and one guy said to the other, "Let's go downtown and get a couple of girls!" So they went downtown that night, but the girls they found thought they were sleazy and decided to play a trick on them by slipping out and sticking blow-up dolls in the beds.
The next morning one of the guys said, "I think my girl was dead, because she didn't grunt or groan when we were having sex last night." The other guy said, "I think my girl was a witch, because when I bit her on the tit she hissed and flew away...."