I had never heard that before but found the story here.
http://rebrn.com/re/happy-birthday-to-this-comedic-genius-849895/
Perhaps some context would have helped. Nevertheless, Rickles and Newhart remained best friends even to vacationing together all around the world.
The quip you quoted would be something I could well imagine Rickles saying. His night club acts were not a brand of humor I appreciated which is why the friendship always struck me as somewhat strange and worthy of note on this thread.
I saw a special on him recently “Mr Warmth”. And it interviewed Bob Newhart. If I recall correctly Bob and his wife had dinner with Rickles and she was commenting how nice he was. And Bob said, “Uh, you know, he’s not like that in his show.” And then they went to the show and Rickles pulls that out.
ROFLMAO.