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1 definition by Wetchman

 
1.
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.
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Mistress: Oh crap - your wife is pulling into the driveway!

Man: The poo-choo train has arrived.

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Co-Worker: Are you ready to leave for the team-building ropes course?
Man: All aboard the poo-choo train.
by Wetchman September 11, 2006