Want to really make a good prank, well then here is one. All you need is a few mateirals and a pillow. :) Enjoy!!
Step 1: Tools
What u need is:
1.Pillow that has a zip and can be placed as a cushion
2.Bag or waterballon(preferibly)
Step 2: How to Do It
1.Take out the pilllow out of the cushion
2. Replace it with a few waterballon or waterbags filled with water(not totally full just enough for it not to be noticed)
3.Close the zip
Make the setting ready and try to make the person whos going to sit on the "wet cushion" to not sit slowly but fast.
Enjoy the moment :)