Season 4: Episode 95: Lush Life
Carrie starts Doug on another new diet which makes him miserable. When Carrie starts the new routine of getting a drink with the girls every night after work, Doug realizes there are real benefits to be had by her "relaxed" demeanor following a little imbibing. Unfortunately, a falling out with the girls ends the ritual, and in a panic, Doug starts to provide his own bar service to Carrie every night in the hopes that the new "happy Carrie who doesn't care if he's on a diet" sticks around a little longer. Arthur also realizes this is a good thing and does his part to keep the drinks coming. Until Carrie finds out.