The Brady Bunch Variety Hour to Third Watch

Both spin offs of The Brady Bunch

Should be The Brady Bunch. The Brady Bunch's Alice crossed over onto Hi Honey, I?m Home!

Alice & Trixie from The Honeymooners crossed over onto Hi Honey, I'm Home!

Here's Lucy's Lucy was driven around Miami by Ralph Cramden of The Hooneymooner's

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

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

The airplane that crashed and strand the cast of Lost was Oceanic Airlines Flight 815 also featured on Diagnosis Murder.

In an episode of Veronica Mars, Veronica's fortune cookie had the numbers that won Hurley from Lost the lottery.

The mugshot of Malcolm T Wiggins from the X-Files episode "Titonus" appears on the wall of a police interrogation room in the Veronica Mars episode "Leave it to Beaver." Also the fictional car rental company Lariat where Mulder & Scully always rented their cars was featured prominently on the Veronica Mars episode "Rat Saw God."

Homicide's John Munch questioned The X-Files' The Lone Gunmen.

Chicago Hope's Jeffrey Geiger accepted an organ of a victim on Homicide

A reporter on Chicago Hope talked to Dr. Austin about having been accepted into the space program and mentions an ER doctor from County was also accepted. In a separate episode of ER Dr. Greene was accepted in the space program.

ER's Dr. Lewis went to New York to look for here sister and was aided by the characters of Thrid Watch.