In Saints Row 2 and Saints Row: The Third, there is a prompt to start this diversion after one player kills the other. In Saints Row IV, it is started from one of the markers around the Simulation.
The goal is to earn more points than the opponent for 3 minutes in Saints Row 2 and Saints Row: The Third, or 2:30 minutes in Saints Row IV, unless one of the players is killed. The winner gets $200.
After the 3 minutes, the Cat and Mouse switch.
Cat[]
The objective of the "cat" in the offensive vehicle is kill their opponent to prevent them from earning points.
Mouse[]
The objective of the "mouse" in the evasive vehicle is to survive for as long as possible, earning 10 points per second they stay alive, as well as 250 for hitting each checkpoint.
While there was a "Cat & Mouse" promo image featuring the F-69 VTOL as the "cat" and the Specter as the "mouse" vehicle in Saints Row: The Third, this combination does not appear in game as they are both offensive vehicles.