Yesterday, I was watching the "That Little Old Matchmaker, Martin!" episode, and during the scene where Tim and Martin are in William Fisher's office, Robert Colbert, as William Fisher says "What is it that I can do for you, Bill?", as he's talking to Tim O'Hara/Bill Bixby.Wouldn't the director, or Bill Bixby caught this? Is this a known blooper?
Robert

Yes, absolutely. It is a well-known blooper of the series. It’s mentioned on my MFM website, on the trivia page.
http://members.tripod.com/~jhh_2/TVMFM.htm

Jharison