Don't be surprised if you see a lot of bare legs on the subway this weekend.
Jan. 12 is No Pants Subway Ride day, an annual event celebrating silliness.
Started in 2002 by the New York-based group Improv Everywhere, this day of riding public transportation pants-less has spread to nearly 60 cities worldwide.
Last year's event in New York City had more than 4,000 participants, according to Improv Everywhere.
As the name of the event implies, participants dress in normal winter attire -- coats, hats and scarves. The only thing missing is their pants.
Chicago's No Pants organizers recommend wearing "granny panties, bower briefs, boxers, boy cut." In other words, something "tasteful and covers more," according to its Facebook page.
D.C.'s organizers remind participants to act normal, "as if you had no idea that you were missing pants or that you knew but didn't think it was a big deal," according to the D.C. Facebook page.
They also tell participants to put their pants back on if an authority tells them to.
"Unfortunately indecency laws are entirely subjective," the page says.