Adam-12 to George & Leo
12 connections
Adam-12
Emergency!
Emergency! had a crossover with Adam-12 to find a boy who ran away from the hospital.
Matlock
Both feature the fictional Trans Global Airlines
Diagnosis: Murder
Diagnosis Murder's Dr Mark Sloan was defended by Matlock when Sloan was accused of murder
Lost
The airplane that crashed and strand the cast of Lost was Oceanic Airlines Flight 815 also featured on Diagnosis Murder.
Veronica Mars
In an episode of Veronica Mars, Veronica's fortune cookie had the numbers that won Hurley from Lost the lottery.
The X-Files
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: Life On The Street
Homicide's John Munch questioned The X-Files' The Lone Gunmen.
Oz
Homicide's detectives watched Oz's Miss Sally on TV.
St. Elsewhere
St Elsewhere's hospital management company Weigert (was Ecumena) took over Oz's hospital.
The Bob Newhart Show
The Bob Newhart Show's Elliot Carlin visited the psych ward at St Elsewhere's St Eligius Hospital.
Newhart
The Bob Newhart Show's Bob Hartley woke up after dreaming the entire series Newhart during Newhart's finale.
George & Leo
Newhart's Dr. Michael Harris visited George & Leo