Betty Jarra, an organizer of the event, which began in New York in 2002 and has spread internationally, said subway riders took to the tubes in their underwear Sunday amid 14-degree temperatures and falling snow outside, TheLocal.se reported Monday.
"It was really nice. We had about 65 people altogether and two more joined in when they saw what was happening," Jarra said. "They just took off their trousers and continued their journey -- and a couple more joined us along the way."
Jarra said some subway riders wondered whether their pantless counterparts were mounting a protest.
"Some people wondered if we were protesting the weather," she said. "But it's not some important political thing, we're just having fun and trying to get a smile out of other Stockholmers. When we finished up with a group photo, there were about 20 other people standing there taking pictures of us."
"A few of them even said they'd join us next year," Jarra said.