A producer friend has passed along a Don Rickles story, told by a person who knew Rickles and Frank Sinatra:

“Rickles and Sinatra were playing different rooms at Caesar’s Palace in Las Vegas one weekend. [Back in the mid ’60s, I’m guessing.] Don caught up with Frank before he went on one night and said, ‘Listen Frank, I’ll be in the audience tonight. I’m bringing a gorgeous girl and it’s a first date and you know I’d really like to impress her.’ Frank said, ‘Sure Don, how can I help?’ Rickles said, ‘Can you come over to the table after the show and say hello and be real friendly? She’ll be really impressed.’ Frank said, ‘Sure, no problem.’

“After the show, Frank made his way over to Rickles’ table and there he was with the girl. Sinatra grins and says, ‘Hey Don! How ya doin?’ Rickles looks up and says, ‘I can’t talk now, Frank…I’m busy.'”