No, not a duet. Somebody posted a single YouTube link with two of my favorite singers in TV appearances from the 1960s.
First Ella Fitzgerald sings her lotsa-fun cover of the Beatles' "Can't Buy Me Love" and then a great version of her "Mr. Paganini."
Then, Ethel Merman lends her brassy approach to two Irving Berlin ballads that are usually done with more, shall we say, delicacy.
(You'll never heard these lyrics the same again after you hear Ethel slam into them: "All by myself / I get lo-ho-ho-nely" and "Waiting for a ring / A ting-a-ling.")
http://youtube.com/watch?v=6gqx2lHOfQQ