When you're having sex with your girlfriend from behind and you spit on her back so she thinks that you've already ejaculated so she turns around. Little did she know that you have secretly hidden your best friend in your closet as he's been watching and masturbating the whole time. You run towards the closet and open it and your best friend flips you for a standing 69. You both then bust in each other's faces as your girlfriend watches in confusion. You then proceed to walk away holding hands with your best friend, leaving your girlfriend behind as if nothing happened.
Yo! I Sidekick Surprised my girlfriend last night with Tron. It was epic.