My husband used to eat a bowl of cheerios every morning. One April Fools Day, we replaced the cereal with those large plastic Easter eggs, and then talked to him (to slightly distract him) while he poured his cereal. The lack of comprehension in his eyes, as he viewed the bowl of plastic eggs, was priceless.

My grandfather did this to my grandmother in the late 1940's. Their first April Fool's Day, he woke up early and made pancakes- and this was a man who never, ever cooked. He made my grandmother some cotton balls flattened out and dipped in pancake batter, then he made some normal ones for himself. Hers were uncuttable (not a word, I know), while he sat there happily eating some delicious pancakes. Ah, family legends....

Last year, I baked a cake and put water balloons in it and had a guest cut it. http://ohmypuddin.wordpress.com/2010/04/02/april-fools/

one year i switched the salt and sugar--sweet scrambled eggs and salty cheerios! my sister ran to the bathroom to brush her teeth right away and she was the recipient of the horseradish i had stuffed in the the tip of the tube.

Not a food prank, but it is a kitchen prank. My husband makes the coffee every morning so before going to bed I carefully aimed the sink sprayer to where he stands every day... a small rubberband around it and whoosh! He turned the water on and instead of filling the pot he got it right in the belly! I probably thought it was funnier than he did but at least he was still wearing his robe.

I made Cake Poops (à la Bakerella's Cake Pops) this year! Pretty delicious and disgusting...

wouldn't work now... we have a new faucet/sprayer combo.

This isn't a mean trick at all, but my sunnyside-up eggs on toast aren't actually eggs:
http://cookistry.blogspot.com/2010/01/whats-cooking-whimsy-in-kitchen.html

Years ago, Oreo had a "spring" cookie with blue filling. One of my co-workers replaced the filling with Crest and left them for an unsuspecting staff person to try. The woman who ate one was NOT impressed. (It wasn't me.) Pretty much ruined the fun for all!

Jalapeno jelly beans, watermelon, and apple flavor all in the same bowl

"Brownies" made out of dry kitchen sponges cut to size and coated with chocolate. A sprinkling of powdered sugar seals the deal :)

When I was maybe eleven, I discovered that water properly mixed with corn-starch looks (vaguely) like milk and decided to serve it to my younger sister with her dinner. It was apparently convincing enough for her to drink it, but wasn't funny enough for my mother not to punish me.

I usually do chocolate covered balls of salt dough (equal parts flour and salt, enough water to hold it together) and leave them around for people to nibble on. I also make a real treat to make up for it

I like the spaghetti tree April Fools, where it was shown on BBC that spaghetti grows on trees.

Well, in the Francophone part of the world, it's called "Poisson d'Avril" (April Fish), which is what you cry out when you pull a prank.

My 7 year old daughter has been plotting somewhat without direction, but 4 weeks ago she *did* convince me to bake fish-shaped cookies, which I just sent off to school (orange cookies, and 2 kinds of chocolate, all drizzled with melted dark and white chocolate; very pretty if I *do* say so myself). Her original idea was to stick jokes on the bottom of each fish, but she didn't come up with the jokes, and frankly, there were too many damned little fish. (I type this still in my nightie and covered in melted chocolate -- maybe the joke was on me... hmm... )

when i was a kid, we took an old cleaned out mustard bottle, put a long string of yellow yarn in the the top (tie a knot at the end so the string doesn't go all the way out). my mom was in on the joke and served hotdogs...as i was bringing the mustard to the table i pretended to accidentally squirt it all over my dad-- the yellow string flies out and looks like mustard at first. it was pretty epic, he jumped up from the table so fast he knocked over his chair.

If you freeze mayonnaise, it looks exactly like vanilla ice cream. I used this prank with some middle school students once and it was priceless!!!

About 10 years ago, a coworker brought in a tray of delicious candied apples--all lovely and shiny...nut covered...stick...the works. However, one of the 'apples' was an onion...which was a bit of a surprise for our CEO who happened to select that one off the tray. An epic workplace moment.

Yellow dish soap carefully mixed in water looks just like Gatorade... just ask my sister!

I introduced Aprils Fool's Day to my 4 year old daughter today. We made chocolate "Dirt Cake" for some of her friends who came over. I know it's not that amazing, but it was so fun to watch her face as she showed the cake (in a flowerpot with tulips stuck in) to her friends.

two of my kids have birthdays in april, which is a great excuse for trick food. little kids are gullible!
one year we served an ice cream cake with cupcakes baked in flat-bottomed cones--the first taste surprised every last kid.
a couple of years ago i made pound cake in a loaf pan, sliced it, and made sandwiches with orange icing. then i served the "grilled cheese sandwiches" to some very confused children who politely told me they'd already had their lunch and they'd prefer cake, please. i couldn't even convince all of them to try the sandwich!

These are absolutely fantastic! I can't wait to prank my boyfriend

We did the frosted sponge trick at work on Friday. Priceless.

Another fun prank - when someone is cooking and also working on another task, systematically hide and then put back their utensils/ingredients/what have you each time they leave the kitchen and then come back. We did this to a roommate once, stealing her spoon, cheese, milk, and then the whole pot of mac n cheese. Lol.

Everyone has written about a so-funny prank they played on others, not something incredibly amusing that was done to them...

On a tip from Martha Stewart Kids (I miss that magazine), I solidified the milk in the breakfast table pitcher with gelatin. My daughter (4 at the time) was so confused when she tried to pour it on her cereal! It's now considered the benchmark April Fool's trick at our house. So far we haven't topped it.