Emmy and Peabody Award-winning animated American sitcom The Simpsons, now an intricate part of American culture, will celebrate its 400th episode on Sunday with the 21st episode of its 18th season. The last episode was about the dog, Little Helper, who became a police dog and then returned to his quiet family life.

As for tomorrow's anniversary episode, it will span across two parts: the first part, "24 Minutes" (8 p.m.) lampoons "24." Reportedly, Kiefer Sutherland, star of "24," voices an animated Jack Bauer who helps Bart and Lisa Simpson foil a plot to set off a stink bomb at their school.

The second part, "You Kent Always Say What You Want," starts with dentist jokes, including a dental hygiene rap by the real-life Ludacris.

The show is created by Matt Groening for the Fox TV Network, who conceived it shortly before a pitch for a series of animated shorts with the producer James L. Brooks. The show's characters are named after members of Groening's family, except Bart, who is supposed to be Groening himself.

Time magazine's 1998 issue named it the 20th century's best television series, and on January 14, 2000 it was awarded a star on the Hollywood Walk of Fame. The series' distinctive theme song was composed by musician Danny Elfman in 1989. This piece, which took two days to create, has been noted by Elfman as the most popular of his career.

Homer's "D'oh!" made it into the Oxford English Dictionary in 2001. All told, the franchise has generated a reported $1 billion in revenue. A feature-length film, The Simpsons Movie, is currently being produced to be released on July 27, 2007.