Wow, it's amazing that I never realized that Stretch Cunningham and Harve Miller were played by the same actor. I just looked up James Cromwell's entry on IMDB, and I see that he has guest starred in lots of TV shows I've watched at one time or another, including Family Ties, Star Trek: The Next Generation, Enterprise, Night Court, Magnum P.I., Hunter, ER, Maude, M*A*S*H, Diff'rent Strokes, and Home Improvement.
There have been at least two other instances of LHotP stars or guest stars that I didn't recognize from other roles until I read about them later -- Bonnie Bartlett, who played Dr. Craig's wife on St. Elsewhere (she also guest starred on Home Improvement, ER, L.A. Law, Golden Girls, and many other shows), and Peter Billingsley (Gideon from "No Beast So Fierce"), best known as Ralphie from A Christmas Story.