Alphas to Remington Steele

Dr Vanessa Calder from Warehouse 13 traveled to investigate deaths on Alphas

On Warehouse 13 Mrs. Frederic and Steve Jinks enter The Library, a secret room in the Vatican. There is a pack of Morley cigarettes on the table

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."

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

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

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 Mary Tyler Moore Show's Georgette Baxter crossed over onto Hi Honey, I'm Home!

Lou Grant spun off of The Mary Tyler Moore Show

Lou Grant centered around Lou as editor of the fictional Los Angeles Tribune which has been featured on Remington Steele