Darrell Hammond resurrected his “SNL”-era Bill Clinton impression at Garden of Laughs at Madison Square Garden on Saturday, talking about all the situations in which people bring it up, including during a colonoscopy and at a drug den. Hammond, who is now clean, told of meeting a man who took him to a crack house where the owner thought he was a cop. “I don’t look kind of like an undercover cop, I look exactly like one,” he joked, saying his companion explained he’d seen him on TV. He added, “Across the room, between hits on a crack pipe, a topless woman went ‘Dat’s Clinton.’ ” Others who performed at the event to benefit the Garden of Dreams Foundation included Wanda Sykes and Ray Romano.