Ep 4. Treehouse of Horror XX

In the 21st season of The Simpsons, episode 4 is titled "Treehouse of Horror XX." This special Halloween-themed episode is the 20th installment in the series of "Treehouse of Horror" episodes, which are often regarded as fan favorites.

The episode is divided into three segments, each parodying a different classic horror or sci-fi story. The first segment, called "Dial 'M' for Murder or Press '#' to Return to Main Menu," is a parody of the movie "Avatar." In this segment, Bart and Lisa are transported to a distant planet where they become part of a tribe of blue-skinned creatures. However, they soon realize that the tribe plans to sacrifice them to their tree god, and they must figure out how to escape before it's too late.

The second segment, titled "Don't Have a Cow, Mankind," is a parody of zombie films. In this segment, a virus spreads through Springfield, turning everyone into flesh-eating zombies. The Simpson family must fight for survival and try to find a cure for the virus before it's too late.

The third and final segment, "There's No Business Like Moe Business," is a parody of the film "Sweeney Todd: The Demon Barber of Fleet Street." In this segment, Homer discovers that his favorite bar, Moe's Tavern, is actually a front for a murderous pie-making operation. Moe and Mrs. Lovett, the bar's owner and chef, have been using their customers as the main ingredient in their pies. When Homer finds out, he must decide whether to join in on the gruesome business or put a stop to it and risk losing his beloved bar forever.

Overall, "Treehouse of Horror XX" is another hilarious and spooky addition to The Simpsons' long-running Halloween tradition. Fans of the show and horror enthusiasts alike are sure to enjoy this episode's clever parodies and witty humor.