Mayberry R.F.D. to The Bob Cummings Show

was a spin off of The Andy Griffith Show

Gomer Pyle, U.S.M.C was a spin off of The Andy Griffith Show

The Lucy Show's Lucy Carmichael was accidentally drafted into Gomer Pyle, USMC's company on an episode of The Lucy Show.

Here's Lucy's Mary Jane Lewis was originally a character on The Lucy Show (also called The Lucille Ball Show).

Here's Lucy's Lucy Carter was visited in two episodes by The Bob Cummings Show's Bob Collins.