You need a screen (white sheet), Flashlight (bright), and a sick (size of a baseball bat).
The announcer introduces the world's greatest pitcher and elaborates on how great he is. No one has hit him in the last 100 games, (at least with a ball), etc. Get volunteers (4). Have the pitcher throw his pitches: (For fun give each volunteer a stick and rubber knife and instruct him to make a baseball bat) Announce each pitch in advance and watch the pitcher throw, followed by light on the screen as the ball advances toward the batter.
1. Fast Ball - Light goes fast across the sheet from the backside)
2. Slider- Light slopes down across sheet from the backside)
3. Curve Ball - light goes crazy
Each volunteer only gets one pitch. Of Course, since no ball is actually thrown, and they can't hit the light so they stand there looking foolish.
The final pitch, the Greatest Ever Spit Ball. Really ham it up. You announce the World's Greatest Spit Ball. As soon as the Pitcher throws the ball you scream, "Look Out It's Out of Control", followed by a bucket of water being thrown upon someone: Your choice, the announcer, pitcher, or batter!
If you are going to get the batter, let the pitcher throw each pitch and announce it as you see it on the screen. The final pitch of course is "Oh no it's a spitball!"