Tell them to watch a video on Youtube and say it's the best Aprils Fool prank you have seen, give them the video then walk away and watch a far distance but it's actually a black screen all through the video so they wasted 30 seconds of waiting to see the video but nothing comes up hahahah! Then you might hear them say hey the video is not playing or the video is not working. It definitely got me!
http://www.youtube.com/watch?v=062DXbENtz8
Old people might have a heart attack with this prank, so maybe stick with the first prank. Anyway tell them you just played this maze game and you can't pass level 3 but in fact it's the scary maze game because as they play the game the volume should be turned up really loud, then on the 3rd level as they are concentrating, unexpectedly a freaky picture comes up and it's screaming so that would scare them really bad like it did to me such a good prank that one! Here is the site to prank them make sure you are there to witness what their face looked like okay? Because it's so hilarious. Also as they are playing say "seriously it's so hard I can't pass the 3rd level" just say you can't pass it, so it makes them determined to do it and because they are concentrating, the prank will scare them even more hahaha! Good luck
http://www.maniacworld.com/maze_game.htm
Even if you can't use these jokes save them for next time!
*I say 'them' because I hope you use these pranks on other people as well!!
Hope you enjoy doing these because it makes you laugh really hard
))