What is it called when you invite people to a party, but the invites are like, one card leads to the next?

They have to like go to a bunch of different places to get different cards, then finally they get the invite. I just need to know what it's called, if anyone knows...
What is it called when you invite people to a party, but the invites are like, one card leads to the next?
A scavenger hunt.
Reply:Scavenger Hunt
Reply:A scavenger hunt?
Reply:It's called a road-rally. A scavenger hunt is when you go to strangers and ask for miscellaneous items from a list.
Reply:domino effect....


snowball effect....
Reply:A scavenger hunt?
Reply:Doesn't sound like a scavenger hunt but more like a poker run.
Reply:what