Allison Janney Plays a Prank on Ellen's Writer (VIDEO)

As she's done several times in the past, Ellen DeGeneres' writer, Amy, helps prank a celebrity on 'The Ellen DeGeneres Show' (weekdays, syndicated). But, this time, the tables are turned on the writer since her target, Allison Janney, is in on the gag.

DeGeneres has Amy prattle on endlessly at Janney, who pretends to be in a bad mood. Then, Janney breaks down in tears and claims to be have been drinking. Needless to say, Amy senses the gag beginning to spiral out of control and reacts nervously as Janney becomes more and more erratic.

Eventually, DeGeneres enters the dressing room and reveals that the joke's on Amy. And, DeGeneres says, she even had Janney take a sip of alcohol beforehand to increase the realism.

Visit 'The Ellen DeGeneres Show' here.