Civil Wars to Make Room For Granddaddy

L.A. Law's firm added attorney Eli Levinson and his secretary Denise from Civil Wars.

Cop Rock's station house was also visited by Victor Sifuentes and Abby Perkins from L.A.Law

Hill Street Blues' Howard Hunter appeared on Cop Rock.

NYPD Blue's station house was visited by Hill Street Blues' Buck Naked

The Drew Carey Show's cast went to NYC where a traffic tie-up was being investigated by NYPD Blue's James Martinez.

The Drew Carey Show did a cross over with Coach.

Newhart's Larry, Darryl and Darryl squatted in Coach's Hayden and Christine's home

The Bob Newhart Show's Bob Hartley woke up after dreaming the entire series Newhart during Newhart's finale.

The Bob Newhart Show's Elliot Carlin visited the psych ward at St Elsewhere's St Eligius Hospital.

St Elsewhere's Dr Turner was investigated for murder by Homicide's Pembleton and Bayliss.

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

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.

Make Room for Grandaddy's Williams had Here's Lucy's Lucy Carter as a houseguest