April Fools prank ideas

There's no cause for alarm -- if the mess isn't real. Mix 1/4 cup white glue and 2 tablespoons puff paint. Place an old mug on a parchment-lined cookie sheet; drizzle the "spill" in and around mug. When dry to the touch (about 4 days), peel away paper; let dry completely, about 1 more day. http://www.marthastewart.com/goodthings/spill-thrills?backto=true
Turn the kitchen sink into a blue lagoon with nontoxic dye pellets, designed to tint children's bathwater. Unscrew the cap on the faucet, and set a couple of the colored tabs inside before replacing it. When the water is turned on, the burst of color will be short-lived yet shocking. (Dye pellets are made by Crayola.)
Transform milk into an unpourable mass: Stir 1 packet of powdered gelatin into 2 tablespoons of water, and let stand for 5 minutes. Warm 2 cups of milk in the microwave. Stir the gelatin mixture into the milk. Transfer to a glass pitcher or bottle, and refrigerate until set, about 2 hours.http://www.marthastewart.com/goodthings/april-fools-trick-solid-milk?backto=true
A mashed-potatoes-and-gravy sundae is a good gag for the afternoon, when everyone thinks the jokes are over.