Note: The April 2011 update is required. Tap the candy on a string hanging out of the "o" in "Rope" at the title screen to turn it into an Easter egg. Start game play. The candy will be replaced by the Easter Egg and Omnom will wear bunny ears when close to the candy.
On the menu screen, tap the candy once to make it turn into a doughnut, twice to turn into a cupcake and three times to make it turn back into a candy. Note: The most recent update is required to do this (and you will not be able to turn your candy into an Easter egg).