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!
Carefully open a small bag of chips by pulling apart the top, then remove the wafers. Replace them with some other type of chip, or fake cardboard "chips." Then glue the top back and offer them to your victim.
Place a "For Sale" a notice on your victim's car. Quote a very low cost, yet a realistic realistic one and don't forget to mention victim's phone number.
Take a slice of cream cheese or jelly and carefully insert it into the deodorant container after scooping about an inch of deodorant from the top of the victim's stick deodorant. Sculpt cheese or jelly well so that it looks like a deodorant. Put the top back on and wait for the fun!
Stuff victim's shoes with some cotton, when the person will try wearing it they will feel that either their feet have swollen or the shoe has shrank.