Brett Leake is an anomaly among modern stand-up comics: He is smart. He does not curse. And he sits down. That last fact is the result of Leake’s “slight disability…a degree in economics.” But seriously, the Richmond native actually labors with a form of muscular dystrophy that affects his performances only in that it provides some good punch lines. With a discerning wit and genial delivery, Leake looks at the tiny yet inescapable incongruities of modern life—the cash value of coupons, for example—and draws out the “Aha!” moments, where you laugh because you think you’ve learned something. Not a common occurrence at, say, a Tom Green show. “My jokes are PBS-clean,” Leake says. “There are nights when Bill Moyers has a saltier show.” Try to keep up with this guy’s big brain when Leake performs at 8:30 p.m. (see City List for other dates) at the D.C. Improv, 1140 Connecticut Ave. NW. $15. (202) 296-7008. (Dave Nuttycombe)