Step 1: walk around a public, open space with 5 people who love ultimate, and a disc.
Step 2: have someone run up to a group of people (more than 3, at least) with pinnies for them to wear
Step 3: return back to classic ultimate line formation, and shout "ULTIMATE" giving the random opponents about 1 minute total to decide whether to fight back or not.
Step 4: if yes, PLAY.
(have a 6th person to film this whole thing, if possible) :)