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!!
Take an empty suitcase. Pick it up and carry it like it is really heavy. Go to the victim and ask them to carry it somewhere for you. They'll be unprepared for such a "light" load.
Keep a spool of thread matching your shirt and hide it in your pocket. Leave a length of thread hanging out. When your victim will see it and try to pull it out. It will keep coming and coming!
Right before a lecture as you are walking into the classroom, ask one of your classmates if they are "ready for the test today?" Involve one more pal of yours in the prank who can authenticate your statement that there is indeed a test that day.
Borrow or steal your victim's car key night before April 1st. Put them in a glass of water and put off the glass in the freezer. In the morning, leave the glass on the table for them. Or, even more devious: freeze their keys in a big bucket of ice!
Add some yellow food coloring to water, and sprinkle it liberally all over the toilet seat and on the floor around the toilet.
Place a stuffed mouse or small stuffed animal inside the victim's cabinet and attach it to a string. Tie the other end of the string to the inside of a cabinet door and wait for your victim to open the cabinet-- the animal will "jump" out on them and give them a good dose of shiver!