If you were riding a subway in a major city yesterday, you might have been subjected to the strange sight of a pack of giggly riders missing their pants. We know this because the evidence of the prank is all over YouTube today.

In commemoration of the 10th edition of "No Pants Day," some very cold looking passengers rode subways, trollies, and metros ...bottomless. Most people point to ImprovEverywhere, creators of the famous "Frozen Grand Central" prank, as the originators of the "holiday."

We've seen hundreds of clips hit YouTube in the past 24 hours. Here's a small selection:

New York	Chicago
LA	Portland

We also saw clips from San Francisco, D.C., and Boston.

"No Pants Day" also spread to London again this year, where for riders on The Tube it's actually known as "No Trousers Day."

ImprovEverywhere says they'll have their official video posted in a week.