Don't have much time to plan an elaborate ruse?  No Problem!  Just use a couple of these classics, and let the hilarity ensue.  In fact, some of these are great even when it's not April Fools Day!

Sure shot: All you need is a rubber band and a kitchen faucet with a spray hose. With the faucet off, wrap the rubber band around the handle to keep it in the on position. Wait for someone to turn the faucet on. Keep a towel handy.

Inactive mouse. Unplug the mouse from the computer. See how long it takes for the computer genius in your house to troubleshoot.

Ewwwthpaste. Stick a raisin (or other edible ugly object) into the toothpaste tube. When squeezed it looks like a bug . . . or something worse. Listen for the exclamations of pure gross-out. This one is especially effective on moms and big sisters.

Color enrichment. Add some food coloring to the milk jug. Explain to your kids that a recent scientific study found that colored milk contains more vitamins A(pril) and F(ool's) than white milk.

Big foot. Stuff crumpled newspaper into the toe of someone's shoes. A good one to play on dad. Apparently, it's not just his gut that's growing.

Wrap seat. Stretch plastic wrap over the toilet seat. Make it as smooth as possible so it's invisible. Word of warning: a mess is inevitable with this one.

Flipped out. Carefully turn the dresser drawers upside down and slide them back into place. This one takes teamwork.

Correction, please. Another one for the computer geek. Use the auto correct feature in Microsoft word to set up someone's computer to automatically replace a commonly typed word like 'the' with 'April Fool's!'
Sleeping fools. If you've got little ones try this: after they've fallen asleep carefully move them into each others' beds. They'll wake up to an April Fool's surprise.