poo-choo

Reference to the train Mr. Hankey rides on in a South Park episode. A cute little song accompanies his arrival on the poo-choo train:

Mr. Hankey: Poo-Choo Train's layin' down its tracks with a -
Train Whistle: poo-choo
Mr. Hankey: - all the way and back!
Cartman: Poo-Choo Train is my favorite thing, spreading Christmas joy as we ride and sing!
Mr. Hankey: Christmastime wouldn't be the same without hugs and kisses and a Poo-Choo Train.

Socailly, Poo-Choo used to express the arrival or existence of something bad or unfortunate.

The repeated ramming of a young lady in her rectum, by not one man. But many men, possibly thousands. The new gangbang.

Lyrics:

Mr. Hanky: "Poo-choo trian's layin' down its tracks, with a POO! CHOO! all the way and back!"

Eric Cartman: "Poo-poo train is my favorite thing! Spreading Christmas joy as we ride and sing!"

Mr. Hanky: "Christmas time wouldn't be the same, without hugs and kisses and a poo-choo train."

Train made out of turds; created by Mr. Hanky on South Park as a way to reach the North Pole.

When sitting on the porcelain throne, preparing to drop some deuces a steady stream of fart air emits from your bunghole, sometimes pinched enough to emit a squeaking or whistling sounding fart announcing the turd train a'comin until the poo seals off the space and stops the whistle

The act of passing a blunt to the other end of the rotation. Making sure everyone is involved on the poo choo express. The first person says all aboard, the second makes the sound of a train starting, the third makes the says chuga chuga chuga poo choo, and so forth till it gets to the last person in rotation, and they makes a train braking sound. If that last person fails to make the braking sound, you'll end up with a train wreck. This also makes it so nobody can double hit.

A sexual act / contest in which three or more men (or women with a strap on) perform anal sex on each other in a line. The member of the train that has the most fecal matter on their penis is the winner. The loser is the person from whom the winner has just removed their penis. The penalty for losing is that the loser must clean the penis of the winner by whatever means the winner requests.