The Flash to The Munsters

Arrow spun off The Flash

Hawaii Five-O references Dominic Alonzo from Arrow

NCIS: LA and Hawaii Five-O worked together in a crossover episode to stop a smallpox outbreak

NCIS: LA was a spinoff of NCIS

NCIS was a spinoff of JAG

Oceanic Airlines

Mannix returned to TV on an episode of Diagnosis Murder to solve an old unsolved case with the help of Dr Mark Sloan.

Here's Lucy's Lucy Carter and Mannix's Mannix are held hostage in an episode of Here's Lucy.

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

Mr. Mooney from The Lucy Show was on Hi Honey, I'm Home!

The Munsters' Grandpa Munster crossed over onto Hi Honey, I'm Home!