If you translated this from French to English, you would get "April fish" or "fish of April". That was what the French class at my school did on April Fool's Day (not sure whether the Spanish classes participated). We cut some fish out of paper and put tape on them, sticking the fish on the backs of unsuspecting students. My teacher even suggested that we try to get teachers, but only the ones that could take a joke.
It is harder to do than it seems. A classmate sitting behind me tried to stick his fish on me several times, but I felt it and pulled it off my back. My classmate attempted on the person sitting next to me, but she thought something was amiss and discovered the fish too. When the teacher came near, one student asked, "Hey, would it be okay to, just hypothetically, stick a fish on your back?" She said yes rather sarcastically before saying no. Then she looked at the person sitting behind me, since he was holding a fish, and said, "Oh no, I'm in the danger zone."
I tried to stick a fish on the back one of my friends, but she noticed, too. It really does take slyness to put a fish on someone's back. (Or you at least need to pick a target that is not particularly observant.) I gave one of the fish to another friend, who then proceeded to stick it in my hair and on my back while I was eating. (Ah, well. No harm done.)
I only made three fish in total, so I had only one left. I wanted to make sure that it would definitely end up on someone's back. At first I tried to stick it on the back of a boy passing by, but then someone came up behind him and looked at me suspiciously, so that was unsuccessful. I decided to try on a classmate this time. He did not notice the fish, so I felt like saying, "MISSION ACCOMPLISHED!" (Excepted in a weird accent like Fox McCloud does in Super Smash Brothers Melee. You gotta hear it someday.)
But then I started to worry. What if he never did notice the fish? What if it ended up in his washing machine? I have no idea what the tape would do to a washing machine. I hope he or his mother noticed it eventually or at least that the fish fell off somewhere. (But it would be a shame if the fish got lost. Ah, well, it's not hard to make anyways, just doodle on a piece of paper and cut it out with scissors.)
My mother says she doesn't understand the point of April Fool's. Sometimes people are made uncomfortable or are even hurt by tricks that were played on them on April Fool's Day. (Personally I've never really had anything bad happen to me, which is a relief.) But it's also a day where we can be mischievous to a certain degree and not get in too much trouble for it. I'd like to play a prank, actually, but it'd probably be too risky, like if I did the old banana peel thing (what if a person broke their tail bone or hit their head and got a concussion? Yikes). But it might be okay to draw on someone's face or something. I actually saw that happen at a place I went to in the summer... I did hear from someone that putting ink on your skin shortens your life by a little every time, though. I wouldn't want to be taking away a person's life. D: Already my life is probably short since I have a long pencil in my pencil pouch and it keeps sticking out of the side and poking me. Not very pleasant.