By all accounts, David Letterman was already having a pretty crappy week before he filmed last night’s episode of the Late Show. Not only was he forced to apologize for his “hikingâ€-related indiscretions, but Robert “Joe†Halderman’s creepy lawyer is threatening to to unveil evidence in a court of law that proves Dave sexually harassed an untold number of his employees. However, all of that pales in comparison to what went down at the end of last night’s program. After an entertaining one-on-one with Paul Shaffer and a mildly uncomfortable interview with Eliza Dushku, star of (the soon-to-be-canceled) Dollhouse, Dave invited the four ancient members of KISS to perform a track from their new LP, Sonic Boom. As Dave walked onstage at the conclusion of their spirited performance, Gene Simmons’s legendary huge tongue snaked out of his mouth and made its way to Letterman’s cheek. Now, that’s just wrong.