From Wikipedia's entry for U.C.L.A.:
The quarterly Undie Run takes place during the Wednesday evening of
Finals Week, when students run through the campus in their underwear or
in skimpy costumes. The run first began in Fall of 2001 when a student,
Eric Whitehead, wearing what he described as "really short shorts"
walked around singing a song and playing a guitar to protest the Police
restrictions on the Midnight Yell. As attendance increased, committees in charge of organizing the event deemed it necessary to employ the UC Police during the event, to ward off vandalism and dangerous activity. In 2007, the route was changed again to begin at Strathmore and Gayley
Avenues instead of Landfair and Gayley Avenues. Tired of the UCLA
administration meddling with in student-initiated, spontaneous
traditions, new finals week celebrations are appearing. One of these is
"Undie Ride," where students ride their bicycles in their underwear on
Tuesday night of finals week.
With the increasing safety hazards and Police and Administration
involvement, a student committee, in order to satisfy concerns but keep
the event, changed the route. It was changed to a run through campus to
the fountain in front of Powell Library. Now It ends with students
cavorting in the fountains outside Powell Library.
[Image via LAist, which has plenty more where that came from]
