The phrase cat’s pyjamas (or cats in pyjamas?) comes from the movie “Zelig” by Woody Allen (1983), where a chameleon-man Leonard Zelig “is literally capable of being any and every man, a human vessel who embodies our sociological urge to conform. He comes to the attention of the public through the media when he is sighted at affluent social gatherings, appearing to some as one man and moments later, as another. In fact, his ability to become everything to everybody makes him a blockbuster celebrity. Zelig’s metamorphosis is material; he physically takes on the ethnic characteristics or manifests the weight proportions of those around him, complete with spontaneous facial hair and costume. The gimmick-crazed public makes him an instant celebrity, and his popularity soars through merchandising tie-ins. A cavalcade of dances, songs and games are created around his phenomenon.” (www.woodyallenmovies.com)
the phrase comes from the 20s and is reportedly adequate to the now more often used:
A bee’s “corbiculae”, or pollen-baskets, are located on its tibiae (midsegments of its legs). The phrase “the bee’s knees”, meaning “the height of excellence”, became popular in the U.S. in the 1920s, along with “the cat’s whiskers” (possibly from the use of these in radio crystal sets), “the cat’s pajamas” (pyjamas were still new enough to be daring), and similar phrases which made less sense and didn’t endure: “the eel’s ankle”, “the elephant’s instep”, “the snake’s hip”. Stories in circulation about the phrase’s origin include: “b’s and e’s”, short for “be-alls and
end-alls”; and a corruption of “business”. (www.yaelf.com)
As for copy cats: it’s someone who copies the words or behaviour of another (wordweb)
