I watched Commish regularly while it was in reruns on Lifetime at the same Highlander was still on. And during that time I noticed that many actors from Commish had a tendancy to show up on Highlander.

Nicholas Lea- played on Commish as a cop and was in two episodes of Highlander. Also he is X-files.
Myles Ferguson- the Immortal brat who showed up twice also was in one episode of Commish.
Ian Tracey- played a Officer on Commish as well as Jonny Kelly in Glory Days.
Peter Outerbridge- played in Reluctant Heroes as well as several episodes of the Commish.
The guy who played the dim witted janitor Freddy played a hood in the Colonel.
There may have been others but I have forgotten who they were.

Brent Stait played D.B. Daven port on Commish and Eddie Doyle on Highlander's Mountain Men.

James Horan played Grayson in Band of Brother's and played Hector Bolcheck in Commish.
Lucas Byron played Josh Cole in Mountain Men as well as Jerr Falcon on Commish.

Steve Bacic played Luke in Little Tin God as well as guest starred on a episode of Commish.

Michael Shanks Highlander's The Zone and Commish's Rising Sun.

There are a lot of connections between "Highlander" and "Star Trek" as well.

James Horan was Lt. Burke in TNG's "Descent"

The actor who played Alexi Voshin was a Bajoran general in DS9's "The Siege" and "The Circle."

Richard Lynch (John Kirin in "A Matter of Faith") played a mercenary captain in TNG's "Gambit"