Players take the roles of characters in some social setting (a diner, a cafe, at college, etc. - decide up front). They take turns telling each other wild and outlandish conspiracy theories. At some point, a player will hear someone else’s theory and find it interesting enough to run with. The person who announced the theory is the Rabbit, and the person who found it compelling becomes a Mole.
At that point, the Mole should immediately narrate a conspiratorial outcome consonant with the Rabbit’s theory. The Men in Black arrive to arrest the group, black helicopters can be seen hovering over head, the character gets a mysterious cell phone call, and whatever.
From that point on, the conspiracy is real. The remaining player characters narrate their actions and the Mole gets to determine what happens in response to that. However, at any time, any player who isn’t the Rabbit can be revealed as another Mole, and join in narrating the conspiracy’s actions.
The conspiracy is not allowed to simply kill the Rabbit. It is only permissible to lure the Rabbit into situations where they would die from otherwise ordinary events, like a car crash or a police shootout.
The game ends when everyone is either a Mole or the Rabbit, and when the Rabbit has either been neutralized by the conspiracy, or successfully gotten the word out.