A Blimp and Fireworks
1. Go to Help>About.
2. Double Click on the the Icon with the Balloon on it.
3. You got a Blimp and Fireworks, the more you click, the more fireworks. You can also move the Blimp around with the keypad.

Hidden Credits
1: go to help / about
2: double click on the image shown in the pop-up window
3: cursor arrow will change into a hand and credits will start scrolling from the bottom of the image upwards.
4: have fun by changing scrolling direction by grabbing the credits roll with the hand cursor