Other than series finales and unplanned on-air births, few television events rival the excitement of the crossover—wherein characters from one program meet characters from another. What are the top-rated TV crossovers of all time?

"The Munsters on Gilligan’s Island" (1964): After winning a contest for a vacation in the South Pacific, an agitated Herman Munster stomps a hole in the plane’s fuselage, sending it careening onto Gilligan’s island. Once there, Grandpa Munster and the Professor devise a potion to transport the monster family home while Ginger poses for photographs on Herman’s bicep.
Approximate Ratings: 240 million viewers

"Frasier Meets The Beatles" (1996): After winning a contest to have the surviving Beatles perform on his radio program, Frasier is a nervous wreck—until the Fab Three invite him to sing all of John Lennon’s parts.
Approximate Ratings: 390 million viewers

"The Simpsons Meet the Simpsons" (1993): Capitalizing off the success of America’s favorite animated family, TV execs logically paired up The Simpsons with the most popular TV show airing at the time—itself. In this hourlong special, the Simpsons win a contest to meet identical versions of themselves, resulting in the two Barts getting into double trouble (also the title of the special’s companion rap single).
Approximate Ratings: 2.1 billion viewers