Once you successfully harvest a pumpkin you can also carve a jack-o-lantern. To do the carving mini-game go into the decorating sceen (where you pick to decorate your garden or screen) and you'll see a picture of the jack-o-lantern in the right corner. Click it and have fun.
Secret Get The Nectar Game
After Harvesting/Gardening all the secret/special plants/vegetables/fruit go to your cute treasure chest open it and click the golden bee at the bottom to play a secret get the honey game.