Since Conan O’Brien replaced Jay Leno as its host, “The Tonight Show” has surrendered its ratings lead to “The Late Show with David Letterman.” I’ve caught more or less every episode since Conan took over in August and, like most fans of his “Late Night” program, I’ve been disappointed by the overall results. I assumed brining Andy Richter back would resurrect some of alternative, zany comedy Conan helmed in the 90s. Not so much. While the off-kilter sketches (“Slipnutz”) and refreshing characters (Crooner Ghost) have taken a back seat, Conan still brings it every night. For example, he’s absolutely hilarious in this segment with molecular mixologist Claire Smith. No, NBC shouldn’t replace him with Jerry Seinfeld.