Working from home today, so I have the TV on in the background. I looked up to see a character on The Rockford Files and wanted to know who he was. Denny Miller. He popped up a bit in various TV shows in the '60s and '70s.
Big blond guy, right? I remember him from a lot of TV. Considering when he was active, it’s amazing he never did Star Trek.
I do remember that when Dennis Miller started acting in the occasional movie, there was a problem because his name was too similar to Denny Miller’s and SAG rules insist on a certain level of uniqueness. Mr. Miller (the younger) was able to argue that he was already established as a public persona using that name.
Then I saw the OP’s mention of The Rockford Files so my next reaction was that the actor who played Rockford’s cop friend (who was named Dennis Becker) was dead. But I checked and that’s Joe Santos and he’s still alive.