Students took over campus for this year's Ditch Day on May 21. It's one of Caltech's oldest traditions—a cross between Animal House and a science fair. One day each spring, kept secret until the last minute, seniors ditch their classes and vanish from campus, leaving behind complex, imaginative scavenger hunts, mazes, puzzles, and other challenges that are carefully planned out to occupy the underclassmen—preventing them from wreaking havoc in the seniors' rooms. In truth, these kinds of hijinks are apt to occur at any time of the year at Caltech, but Ditch Day inspires some of the most inventive manifestations of Techers' notorious pranking impulse.

A History of Pranking
Pranks are common practice at Caltech, often involving rivalries between student houses. Techers have been known to take their hijinks off campus as well. Two of the most famous of these pranks are the changing of the Hollywood sign to read "Caltech" and the rewiring of the scoreboard during the 1984 Rose Bowl game to show that Caltech was trouncing MIT (actually, UCLA was playing the University of Illinois). During the 1961 Rose Bowl Game, Caltech students altered the University of Washington's card stunts to display "Caltech."

Prank the Ones You Love
After four years working with the Office of Undergraduate Admissions as tour guides and bloggers, Caltech seniors Andrew Freddo and Dannah Almasco decided to show their love for the office's staffers by giving them a fake Ditch Day all their own.

Room Stacking 101
The original Ditch Day "stacks"— a Caltech euphemism for "locks"— were devices installed, or measures taken, by seniors to keep underclassmen out of their rooms when they were off campus for the day. (Stacking was also an extracurricular activity that could be undertaken any time, not just on Ditch Day.) Traditionally, there were three different kinds of stacks, each named for the approach required to undo it.

Imaginary Students/Imaginary Lives
Caltech students have the reputation of being intellectually creative, and one of the ways they display it is through the imaginary students they have conjured up over the years.

Other Caltech Traditions
Traditions abound at most colleges and universities, but at Caltech, they don't center on the typical fight songs and mascots. Each of the student houses has its own unique customs. The Flems, for instance, fire off their cannon after graduation each June, and every Halloween, Dabney House stages a pumpkin drop from the top of Millikan Library, the highest point on campus. (According to tradition, a claim was once made that the shattering of a pumpkin frozen in liquid nitrogen and dropped from a sufficient height would produce a triboluminescent spark.)

Ditch Day on Flickr
Email your photos of Ditch Day antics to Caltech's Flickr page. Enter the title of the image as the subject and the description in the body of the message.