Mexican Stingray
After a woman performes a Dirty Sanchez on a male, the same male then takes his index finger and gets as much of the feces on his finger as possible with one swift swipe of the finger and then in one calm and quick movement puts that same finger into the girls anus as he does her from behind.
Instead of keeping it simple, Brad tried to impress Stacy with how quickly he could transition from a Dirty Sanchez to a Mexican Stingray. Stacy was very surprised.