A bunch of people saw Community and decided to invent Mexican Halloween online, not realizing that Mexican Halloween is not a sexual act, but a sexual position.
Note: The chili con carne can sometimes be replaced with salsa sauce.
2: I'm sorry, my boyfriend Mexican Halloweened me and I had to clean my back. Some even got on my bed.
The act of performing a drug deal with someone of mexican descent.
Alan asks what that was about, Berta replies "It's Mexican Halloween".