Conversation so far:
What does Kenneth what is the frequency refer to?
Rather was attacked and punched from behind by a man who demanded to know Kenneth, what is the frequency? while a second assailant chased and beat him.
When was Dan Rather attacked?
On October 4, 1986, while walking along Park Avenue to his apartment in Manhattan, Dan Rather was attacked and punched from behind by a man.
What did the attacking man do to Dan Rather?
As the assailant pummeled and kicked Rather, he kept repeating the question.
What did Dan Rather say about the incident where he was attacked?
Rather said I got mugged. Who understands these things? I didn't and I don't now. I didn't make a lot of it at the time and I don't now...“
Did they find the criminals who attacked Dan Rather?
In 1997, a TV critic writing in the New York Daily News solved the mystery, publishing a photo of the alleged assailant, William Tager.
Did the saying Kenneth, what is the frequency become well known?
The phrase became a popular-culture reference over the years, such as in a scene in the graphic novel Like a Velvet Glove Cast in Iron by cartoonist Daniel Clowes.

Question: What other people started using the phrase?
Self-contained rewrite: What other people sarted using the phrase Kenneth what is the frequency?