It's Lonely on the Top - S11.E22

Because of Woody's civic election win, Sam needs another bartender, a job he gives to Carla. To celebrate, Carla whips up a batch of one of her powerhouse drinks for the guys. The day after, everyone has a hangover. What's worse, Carla, who imbibed and got drunk herself, has a sneaking suspicion that she took someone home and slept with him, that person she believes being one of the Cheers regulars. She confides in Sam alone, and after he tells her it wasn't him, she panics and they both ponder who it could have been, with her worse nightmare having it be Cliff. When her bed-mate ultimately reveals himself, Carla and Sam have to decide how best to handle the information. Two other revelations come to light in the aftermath of the drunken spree. And Sam makes an admission of his own to Carla to make her feel better about her own further revelation.