OK so I get about 3 emails a day asking about staining powders... We might carry them but you can actually get the Most common one Methylene Blue at your local fish supply store or in your science room at school. Methylene Blue in itself is non toxic and a few drops is all you need to have some fun at your drunk friends expense.
First find your Rube. A trusting friend that can take a joke is a good way to go..
Then create a distraction, 12 pallets covered in gasoline should work. Quick! now's your chance, just add 2-3 drops when he isn't looking.
Watch it! watch it!
Now let them get their party on. Oh this is great...Wait is that girl licking her plate? Sexy!
If you put enough in there the end result will look like this. No that is not a toilet tablet, its pee.