1. they look similar. then it's just a tribute.
2. it's a threesome
3. they're twins
4. it's with a celebrity
5. you spread peanut butter on your balls and your dog licks it off
6. you don't look them in the eye
7. you don't remember
8. you get away with it
9. she says it's ok
10. you go home afterwards and fulfill your duty.
11. it's with royalty
12. you have two girls at the same time, so one invalidates the other.
13. you can please all of them
14. you're in a different area code, not to mention a different state.
15. it was actually them but you were thinking of someone else
16. It's in a different ZIP code
17. she's not human.
18. they're on top
19. you get paid
20. you change the sheets afterwards.