The primary rule of the nuclear back-packs in Ghostbusters translates well into a toilet game where you both piss into the same bowl. If you do cross the streams, you must both squeal as you undergo an imaginary process of total particle reversal. This means getting a lot of piss on the walls, so it is best not to cross the streams.

I invented this game.

You can't have done, because I did.

Everyone did. I know I did.

aka Cross Fires. With Cross Fires you can have up to four players. Any more and the whole situation becomes unmanageable.

This was also known as Jesus' Cross - when streams were crossed, each participant would shout 'Jesus' Cross' as loud as possible, so that everyone in the surrounding area would know what had occurred.

Buchan you're a liar. You didn't invent this game because it is a blantant rip off of light-sabre fighting. Everybody knows Star Wars predated Ghost Busters by years you spaz. The game was made all the better by making light sabre noises when the streams clashed.

Also "cross swords". In a Blur video my mate had, Damon and Alex play cross-swords in a motorway service bogs. No wonder Graham quit.