I was just watching an ep of
Barnaby Jones that I recorded this morning and imagine my surprise when John Karlen popped up in a small role as a fence named Easy Eddie. It came as a surprise because his name didn't appear in the opening credits - he wasn't billed until the end credits.
In case anyone would like to watch out for it if it should happen to run on MeTV again, it was the 15th ep from Season 6 and was called
The Scapegoat. IMDb even has a photo of Karlen from the ep
here.