Pizzicato Pussycat (1955)

Mr. and Mrs. Jones hear a piano being played in their living room. They automatically assume it is their cat who is making the music, when in fact, the talented one is a mouse whom the cat has forced into being his stooge to make him famous. The cat is showered with media attention and set to play at Carnegie Hall, where he hopes nobody will notice that he is pantomiming the movements with the keys while the mouse is playing his miniature piano inside the full-scale model.