Some sort of sexual position as stated by Señor Chang and confirmed by Troy from Community.
Señor Chang: Which is actually quite offensive to people familiar with Mexican Halloween as a sexual position.
Troy: *nods head*
A suggestively named fictional sexual position, referenced (often as a joke) in a TV show or movie, which then takes on a life of its own, and is created. A previously successful example is the Venus Butterfly; an unsuccessful example is the Guatemalan Face-hat.
Just put a name, place, or nationality together with any other noun, call it a sexual position, and people will either claim to have done it, or will invent it - Mexican Halloween all over again
Another name for the (fairly uncomfortable) Bermuda Triangle sexual position, so called because the triangle between the woman's arms, her back, and the man's stomach resembles a chip.
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.
A Mexican Halloween is a sexual act. It occurs when a man is having sex with a woman from behind and upon ejaculation, he opens up a can of chili con carne he had hidden earlier, and throws the contents of the can onto the woman's back.
Note: The chili con carne can sometimes be replaced with salsa sauce.
1: Why are you late?
2: I'm sorry, my boyfriend Mexican Halloweened me and I had to clean my back. Some even got on my bed.
Popularized by the program Two And A Half Men
(Season 9, Episode 10, The war against gingavitis):
The act of performing a drug deal with someone of mexican descent.
Berta's doorbell rings, she hands over a package, receives some cash in exchange and says "gratsias, adios".
Alan asks what that was about, Berta replies "It's Mexican Halloween".
a man has anal sex with a woman while a costumed person eats candy from her vagina
my vag is super sticky from that mexican halloween party last night, but that's nothing compared to the pain in my ass!
The act of dipping your cock and balls in caramel and then having your girlfriend lick it off wearing a Lucha mask.
I asked my woman if she wanted to bob for apples last night. She one-upped me by adding caramel and a Lucha mask. Turns out it was a Mexican Halloween!