I just caught my first episode of Black Sheep Squadron, and I liked it.
I noticed two actors who would go on to Magnum PI on this show. Larry Maneti and the guy who played Mac (don't remember his name and didn't see it listed on IMDB so I don't know if he is a regular or just a guest apperance).
I love catching these old series and seeing actors who were stars in later series. It is fun to watch them when they weren't well known.
Jeff MacKay (who played Lt. Don French)is who you're thinking of. There was an episode where French's father came to visit and it was revealed that they were from my home town! (Riverside, California)
Probably the biggest star post-"Black Sheep" would be John Laroqutte.
I think the biggest guest-star who came on the show was musician Peter Frampton (it was the only episode my older sister wanted to see :-)
"It's a trap!"
- Admiral Ackbar
Here are some of the Actors who appeared on Baa Baa Black Sheep who went on to other things:
Larry Manetti - Rick on Magnum, P.I.
Jeff Mackay - Extra on Original Battlestar Galactica, Mac on Magnum, JAG (Master Chief Roberts)
W.K. Stratton - Magnum P.I. (Pilot), JAG, NCIS Pilot
John Laroquette - Night Court, West Wing
James Whitmore Jr - Magnum, P.I., Airwolf, etc
Dirk Blocker - Many TV Appearances (Father was Dan Blocker, Hoss on Bonanza)
Dana Elcar - MacGyver, Double for General Hammond on Stargate: SG-1
Robert Ginty - Many TV Appearances, Director, Artist, Aviator
Joey Aresco - TJ Hooker, Night Court, ST:TNG, Hill Street Blues, CHiPs, etc
Simon Oakland - Many TV Appearances
Red West - Former Bodyguard to Elvis (along with his brothers), many TV appearances