Huff to The D.A.
8 connections
Huff
The X-Files
Morleys
Veronica Mars
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."
Lost
In an episode of Veronica Mars, Veronica's fortune cookie had the numbers that won Hurley from Lost the lottery.
Diagnosis: Murder
The airplane that crashed and strand the cast of Lost was Oceanic Airlines Flight 815 also featured on Diagnosis Murder.
Matlock
Diagnosis Murder's Dr Mark Sloan was defended by Matlock when Sloan was accused of murder
Emergency!
Both feature the fictional Trans Global Airlines
Adam-12
Emergency! had a crossover with Adam-12 to find a boy who ran away from the hospital.
The D.A.
Adam-12 had a two part crossover with The D.A.