PHOENIX -- "Your underwear is showing" was a theme taken to the extreme by one group of Metro Light Rail riders Saturday afternoon in Phoenix, KPHO reported.

Nearly 100 Valley residents celebrated the global "No Pants Day" by hitching a ride on the new rail system and "forgetting" to wear pants.

For the past seven years, national group Improv Everywhere has held an annual "No Pants Day" on which the group rides pants-less on the New York City subway system, and this year, the event went global.

Jeff Moriarty, the Phoenix event's organizer, said the new Metro Light Rail system gave the Valley an opportunity to join in.

"We think it is a fun way to celebrate Phoenix's light rail, and give people a chuckle along the way," Moriarty said.

The event, which was primarily organized online, started at 3 p.m. when the first group of riders stepped onto the train at Dorsey and Apache boulevards. The second group joined them at 38th and Washington streets.

"The train was absolutely packed solid," Moriarty said.

After the first ride, the group headed to Lux Coffee Shop, where the pants-less riders relaxed for a time.

Said Moriarty, "Everybody at Lux got a big kick out of it."

Those who were unable to participate in person followed along with Twitter, a microblogging service, using the #nopantsaz tag.

Pants-less people riding the trains included the text "#nopantsaz" with every message they sent. The messages contained links to pictures, overheard statements and random comments about the event, among others.

Charlene Kingston was one of the people who followed "tweets," or messages, from the participants.

"I didn't expect the online excitement within the Twitter community throughout the event," she said. "The tweets from the group let me feel almost like I was there, except with warm legs."

Kingston also said the pictures were "priceless" and the messages about comments overheard on the trains were "hilarious."

"It makes me happy to live in a town where such good-natured foolishness happens," she said.

And as for the riders?

"Just about everybody had fun," Moriarty said.