The "Odd Quad" is the more commonly used name for the Berkshire Quad, the easternmost group of buildings on campus. It is made up of two freshman dorms, East and Fayerweather, and three upperclassman dorms, Currier, Fitch, and Prospect, as well as the Hopkins Observatory.
How the Odd Quad got its name is a mystery shrouded by time - some say it was simply due to having five dormitories (i.e. an odd number); others suspect it has more to do with the nature of the inhabitants, as the Odd Quad tends to be home to the campus's largest collection of freaks, geeks, nerds, and people who generally consider themselves to be a little...well, odd. If you brought a cape to college "just in case," you're likely to fit in well there. (If you think capes are for losers...you're still reasonably likely to fit in well there. The cape-wearers are still a minority, but a slightly more visible one than elsewhere on campus.)
Odd Quadders tend to eat their meals in Driscoll, the most convenient dining hall, located next to Fitch and Prospect. Driscoll was known a few years ago for the "Driscoll Deviations," a popular series of pranks pulled during dinners by a large group of students.
Some of the best features of the Odd Quad are the Currier ballroom, which features arguably the best (if the most beer-soaked) piano on campus, the roof of the observatory, which has a truly lovely view, and the perfect-for-snowball-fights Eyes located on the western side of East.