Many of Bob Newhart's early stand-up routines involved him talking on an imaginary telephone. You heard his side of the conversation but not the other person. Before him, Shelley Berman did some popular stand-up routines talking on an imaginary phone to an unheard party. Well actually, Shelley usually did his sitting on a stool but it was the same idea. Mr. Berman was known to suggest that Mr. Newhart had cribbed the idea from him.
Shelley Berman was by no means the first comedian to do such routines. He might not even have been the thousandth. Just to name three, there was Arlene Harris, a popular radio comedienne…there was Georgie Jessel talking to various folks including his mother…and one of the oldest comedy records was a thing called "Cohen on the Telephone," recorded in London by Joe Hayman in 1913. Others recorded their version of Hayman's routine and you can hear one from 1916 on this Wikipedia page.
So Shelley Berman didn't invent that or even come close to inventing that. Now, is it possible that Bob Newhart got the idea to do routines like that from Berman? Sure. It's also highly likely that Warner Brothers Records decided to take a gamble on putting out an album of Newhart routines because they saw the sales figures on Shelley Berman's albums. But that's not plagiarism or theft or anything of the kind. It's just kind of how show business has always worked.
Folks on the Internet have been arguing over whether Shelley Berman's claim that Newhart stole from him has any merit and I've been asked my opinion. My opinion, as you can see, is "Not really."