Use a universal remote control system and change the channels and adjust the volume while hiding outside the window of victims room.
An appliance timer is great fun for anyone who wants to pull a great April Fool's Day joke. Try combining one with several items (radio, TV, bright light, etc.) using a power strip. Of course you want to set it up to go off in the middle of the night!
Post signs on a park bench that say,"Caution: Dry Paint". Sit down next to the sign. Laugh at people who come and try to tell you not to sit there!
Find a small picture of a a funny creature ( monkey , donkey , baboon, etc) and use a glue stick to place it over the photo on victim's driver's license. Then send them out for beer, or have some better excuse to send them somewhere where they need to show their ID.
Ask a pregnant woman to take a pregnancy test for you, then bring it home and leave the stick in the washroom for your husband to find.
Leave a pack condoms in your girlfriend's purse. And while looking for something in the purse, take out the condom and create scene.
Puncture the straw with a pin, then offer it to your victim. They'll suck and suck but will only get the air.
Attach two way tape to a long piece of toilet paper and leave it on the floor for your victim to step on.
Cover the hood of your victim's car with think plastic sheet, tucking the edges well under the hood so that it's not visible in first instance. Then paint some funny graffiti or message on the plastic with paints. Hide nearby to see your victim's face when they see the "damage."
Draw a moustache on the face of the person whom you know is sound sleeper ,but while he is asleep! Just use an eyebrow pencil or other make-up. No markers! They're too hard to remove!!