September 1999 and May 2000.
September 1997 and May 1998
September 1997 and May 1998
October 11, 1990 and May 9, 1991
September 24, 1992 and May 13, 1993
August 23, 1998 and May 16, 1999.
September 4, 1994 and May 21, 1995
September 17, 1995 and May 19, 1996
Ringo was the first Beatle to appear in the Simpsons (he was the first major celebrity to appear in the series) in an episode called Brush with Greatness.Paul and Linda McCartney appeared in Lisa the Vegetarian.George appeared in Homer's Barbershop Quartet.
He was one of the first characters
November 1996.
Series 5 (Matt Smith's first Episode)
The Eleventh Hour