Oh crap - I just did a search on Alta Vista, and I'm right.

"Meet Cathy, who's been most everywhere from Zanzibar to Barkley Square,
But Patty's only seen the sights a girl can see from Brooklyn Heights,
What a crazy pair!

But they're cousins, identical cousins, all the way.
One set of matching bookends, different as night and day.
While Cathy adores a minuet, the Ballet Russe, and a crepe suzette,
Our Patty loves to rock and roll-- a hot dog makes her lose control--
What a wild duet!

Still they're cousins, identical cousins, and you'll find
They laugh alike, they walk alike, at times they even talk alike,
You can lose your mind, When cousins are two of a kind!"