A list I consult shows that actress Myrna Loy was among the entertainers who appeared at Expo '74. I have no idea what she did here. The SR's clip files might answer this. But I prefer to imagine that she cheerfully stood on a stage and allowed people to call out requests.
"Hey, Myrna. Remember that scene in 'The Best Years of Our Lives' when you are in the kitchen and you call out 'Who was that at the door?' and neither of your kids answers and it dawns on you that, Al, your husband, is, at long last, home from the war? Could you recreate that for us?"