Judd Apatow made a short documentary of the friendship between Bob Newhart and Don Rickles.  It doesn’t seem like they’d be friends, but seeing them together, it obviously works.

NewYorker: Bob Newhart and Don Rickles

NewYorker: Bob Newhart and Don Rickles

“I love that they became friends because they both played Vegas and neither wanted to cheat on their wives,” Apatow said.