A friends wedding is coming up. One of a tradition here in Germany is the so called "Polterabend". The night before the couple gets married their friends will come to the house of the bride's parents and through china into their front yard. Broken crockery brings you luck.
Nobody is invited to the party but everybody is welcome. Often there will be a little announcement in the regional newspaper to tell the date and the place, as it is held somewhere else than the bride's parents home. Friends, former classmates, neighbours, colleagues from work and more or less everybody you know our knew will be there at least to congratulate. There will be small snacks and beer and of course music.
Everybody is welcome to through and break china. Glass and mirrows are forbidden to through, of course, as that would be for bad luck. Wash bowls and toilet bowls (clean ones!!!) are also thrown very often as it is also china, it breaks and it seems funny. (and for those who throw it, it is an easy way to get rid of it...)
Bride and Groom have to clean up the mess of all the broken things together. In former times the party wouldn't start before they haven't cleaned up everything.
The origin of this tradition is unknown, probably Germanic or heathen.
Germany is, as far as I know, the only place where a "Polterabend" is held and this tradition is alive.