What is the paino song in Superman Returns?

When the child and Lex Luthor are sitting at the piano, playing that simple song.. what is the name of it? I believe the same song was in Tom Hanks' BIG, when he and his boss were on that floor mat keyboard in the toy store. I know that it is NOT "Chopsticks", a.k.a. "The Celebrated Chop Waltz", it's the other one they played...