Something to do with baseball and entertaining the crowds! I don't really understand cricket to any great degree so there's no hope of me going into detail here.
"In 1959, Eddie made his last public appearance, dressed as a Martian and appearing out of a flying saucer at Comiskey Park in Chicago. He presented his Martian ray gun to White Sox players Nellie Fox and Minie Minoso"
...... according to one website. Now you know as much as me. Still, great images.