About 35 people participated Saturday in "No Pants Day" on the L, an event organized by a New York-based improv group called Improv Everywhere.

Similar stunts were also planned for Saturday in New York, Boston and Washington, D.C.

Pantsless riders rode from Granville to Monroe on the CTA's Red Line and back again, seemingly oblivious to the fact that they weren't wearing trousers.

Some even carried briefcases and newspapers while wearing dress shirts and ties.

Shocked CTA riders who weren't in on the joke stared, laughed and made snide remarks, while others, such as Anna Looker, kept a straight face, as if nothing were out of the ordinary.

"It's sort of funny, but people on the L are used to ignoring everything ... even pantsless people on the L," said Looker, who was sitting across from two college students casually chatting about books in their skivvies.