The joker his a mob bank in the beginning. For his getaway, he has a minion back a school bus into the bank, severely damaging the bank. He loads up the money, drops a smoke grenade and leaves, scot free. The bus joins a long line of school buses going by and the cops are never the wiser. But I couldn't help but wonder why the bus the joker's bus pulls in front of never seems to have any reaction. A swerve perhaps, something to note that "holy crap an indestructible bus just pulled out of the bank."