Knock knock. Who's there? Chelsea. Chelsea who?
No, make that Chelsea why? The answer to the question posed in NBC's squalid new sitcom Are You There, Chelsea? (8:30/7:30c) is "not really." Based on late-night spitfire Chelsea Handler's potty-mouthed party-girl memoirs — but dropping the Vodka from the title because that might be, you know, offensive — this smutty but toothless misfire puzzlingly reduces Handler to a supporting role: that of a mousy, whiny born-again sister to the fictional Chelsea, played by That '70s Show's Laura Prepon with a one-note husky-voiced crassness that grows stale long before the first scene (in a women's jail cell) ends with Glee's Dot Marie Jones leering at Chelsea. Which is maybe the only sexual advance Chelsea spurns. As long as she can be on top. Which she mentions a lot.