From Webkinz Insider Wiki
This game is an hourly activity that appears at least once a week in the Today's Activities page.
How to Play
You have five tries to try to throw a ball and hit a target to dunk Wacky Zingoz in a dunking machine. To control the ball, use your mouse for left/right positioning and watch the power meter for strength. The ball goes closest to the center if the arrow on the power meter is a little above the exact middle. If you hit the target, you win 30 KinzCash or a trophy (see below).
There is a randomly-awarded trophy for this game. According to the game instructions, the trophy is awarded if your throw matches the number of the Lucky Dunk for that hour. The chance of winning this trophy is about the same as the chance of winning a Quick Draw.