"Feast of Alvis" is the Christmas episode of Sealab 2021.
In a long cutaway intro, Capt. Murphy tells the story of birth of Alvis to his crew members. The story prefaces the bulk of the episode, which concerns the (failed) attempt to put on an Alvistide pageant. This is cause for many complaints from the crew that do not want to participate due to conflicting religious beliefs. The pageant preparations begin to fall apart, culminating with a fire. In the ensuing panic Capt. Murphy is knocked down, incurring a sizable head injury. As he gets up, cursing his luck, he sees a vision of Alvis himself, who performs the "miracle" of changing eggnog into whiskey, while also admitting to having "crapped" the buffet. During the credit sequence it is strongly implied that Murphy's "holy visitation" by Alvis is merely the result of a concussion.