On the topic of impregnating his wife, comedian GREG FITZSIMMONS wrote in an article for Playboy, "We don't need to be limited by my 5'8", 150 lb., C+ average DNA. Not when five hundred bucks will get me a fistful of Harvard sperm." It's that self-deprecating sarcasm that Fitzsimmons has charmingly mastered as both a writer and performer. He's a veteran of Leno, Letterman and O'Brien, not to mention a regular contributor to VH1's "Best Week Ever." He'll be at the Punchline Fri.-Sat., NOV. 7-8. $20. Fri., 8 and 10 p.m.; Sat., 7, 9 and 11 p.m. 280 Hilderbrand Drive. 404-252-5233. www.punchline.com.