I attended a casting call. It starts with a long application. Weird, embarrassing, crazy things, self-portrait, poetry, what you'd do with $3 million, have you been convicted, things like that. Then, a 30-question quiz, 3 choices for each question, some pop culture. It was about 10 minutes. While the quizzes were graded, the 70+ of us each gave a 15-second bio (what do you do, what you'd do with the money, etc.)
Then, some game play. Two of the production people played as contestants. We were "the mob", each of us with three cards in front of us (numbered 1, 2, or 3). Mob members needed to answer correctly to stay in the mob. A right answer from the player meant the player stayed in the game. The pot would go up for every 10 mob members eliminated. Once the player missed, the pot would be evenly distributed to the mob members remaining.
They had a scale on a whiteboard like this:
Audience Remaining: Amount
90: $1,000
80: $5,000
70: $10,000
60: $25,000
50: $50,000
40: $100,000
30: $200,000
20: $300,000
10: $500,000
0: $3,000,000
The player had three uses of the "panic button" available in lieu of answering the question. The first use dropped the top prize to $2,000,000. The second use cut all money amounts in half, and the third use cut them in half again. (Edit: Also, if the player used the panic button, any mob members who got that question wrong would not be eliminated.)
No word about whether a mob member would be picked as the next player, but as long as you kept answering questions correctly, you could continue playing.
Two games were played, one with easy questions, another with harder ones. I managed to stay in the mob both times, which would have netted me over $33,000 if it were for real.
We were encouraged to yell at and otherwise taunt the player. To me, the game felt like a cross between DOND and a Jerry Springer show, something where an amateur host may have difficulty managing the audience.
As far as actually making it on, I don't know (don't call us, we'll call you).