As I boarded the train at the MacArthur BART station in Oakland around 1:00 p.m. last Sunday afternoon, I realized that the group of people in front of me was dressed in an odd fashion; they were not wearing pants.

Improv Everywhere held its 13th annual ‘No Pant’s Subway Ride’, which took place in 60 cities in over 25 countries around the world.

The event started out as a prank in New York City with just seven men. The idea behind the subway ride is simple: The participants do not behave as if they know each other, they can wear whatever they want to wear, except pants.

As I took my seat, the pant-less passengers stood in front of me, holding the railings above their heads, talking and laughing with one another in only spandex one another in only spandex shorts, underwear, or lingerie items.

When I approached a girl in red lacy undergarments and asked her why she wasn’t wearing any pants, she looked at me like the question I was asking was absurd, which it was, and asked me in return, ‘why are you wearing pants?’

This question sparked similar responses from other pantsless passengers, such as ‘Is there a problem that I am not wearing pants?’ ‘I gave up pants for lent’ and ‘It’s a nice day out, I just wanted to feel the rays on my skin.’

When I approached BART rider Jacob Johnson and asked him why he wasn’t wearing any pants he replied ‘I just forgot them; so did a lot of other people.’

The conversation kept spinning in circles until I eventually caved in and started laughing at the remarks I was receiving. When I arrived at the Montgomery Street BART station in San Francisco I realized that these passengers were just not wearing pants because they didn’t have to, or want to.

The unusual outfits such as a person in half-business suit attire and a person in Batman underwear and matching socks, caused passerby’s to stop their daily routines and enjoy a moment of laughter.

“We don’t do it for any particular purpose, just to give people a smile, make people laugh and make them think,” said Vivek Kramachadran, an Improv Everywhere participant in San Francisco.

Improv Everywhere is a nonprofit prank group that was formed with the mission of ‘causing scenes of joy in public places’. Charlie Todd created the group in 2001 and its ‘No Pants Subway Ride’ spread international to nine cities in 2008. Since its formation, Improv Everywhere has gained 4,000 participants and has executed over 100 missions.

“We do things that are out of the ordinary, that are pranks, but when people think of pranks they think it’s something mean spirited or humiliated but these are things to make people smile and give people a good story to tell,” Todd said in an interview on the Today Show. “The idea is to take a boring place, like the subway at 8:30 in the morning and try to get people to laugh and smile and do something hilarious.”

Unlike a lot of televised prank shows, Improv Everywhere doesn’t reveal their pranks to the public after they are committed.

In November 2011, the group staged a prank at a Best Buy in Manhattan, where 80 participants went into the store wearing a blue shirt and khaki pants, mimicking the worker’s uniform.

They were told to go into the store one-by-one and help out anybody who asked for it without revealing that they didn’t work at the store. If an employee approached them, they were told to say they were just looking for something in the store and it was only a coincidence they were wearing the same clothes as them.

When all 80 of the participants had entered the store, the manager became irritated and dialed 911 in attempt to make them leave. The police arrived and searched the participants but didn’t find anything. Instead, they found the prank hilarious and told the employees of the store that they could not arrest anybody for wearing a blue polo shirt.

More pranks can be found in Todd’s book “Causing a Scene,” which serves as an impromptu guide on some of their most well known pranks.

The book exposes the group’s most well known pranks such as ‘high five escalator’ and ‘frozen Grand Central.’ It promotes the mission of spreading a moment of laughter to the life of busy city dwellers.