Original network: ABC (1960-1965)
Moved to: CBS (1965-1972)
How it fared: Despite bringing in healthy ratings in its first several seasons on the network, ABC's refusal to finance the extra cost of filming in color prompted a move to rival network CBS, where the series continued to flourish for seven more seasons. The show ended its life as one of the longest-running sitcoms in TV history, with 12 seasons and a whopping 380 episodes under its belt.

- Chris Eggertsen