Continuity mistake: When Frank, Charlie, and Dennis are in the cop car at the red light, they're on a one-way street, with cars parked to their left (facing the same direction as the cop car). However, when it cuts to Frank, we see a car drive by in the opposite direction, and the parked cars are gone.
Factual error: Charlie drops the moltov cocktail into the police car in the end, light enough so that it doesn't break, but the car explodes about ten seconds later, as Charlie explains he had soaked the entire inside with gasoline. However, there realistically wouldn't be such a long pause as shown in the show for the gasoline fumes to ignite. Also, the explosion is much more powerful than it realistically would have been, revealing pyrotechnics were used. Obviously done for comedic value, but still a mistake.
Continuity mistake: At the end of the episode, when Charlie leaves the envelope marked "4 the Mare" outside the Municipal Building, as he walks away we see a janitor come by and throw the envelope away. However, seconds later when Charlie jumps into the air, we see the janitor walk and bend to pick up the envelope again.