If Batman still had any Gas Grenades remaining at the end of the fourth stage he shall automatically lose them at this point as the Batmobile's crosshair cursor materializes in the centre of the screen; the premise of the stage is identical to the second one but the cars you must shoot are the Joker's green ones (as opposed to the Grissom gang's black ones), and the red and blue ones are again indestructible. Their point values are also the same as those of the Grissom gang's (100 for the first car destroyed, 200 for the second and so on up to 1000 for the tenth) - but if you again fail to destroy one before passing it, their value shall, like that of the Grissom gang's cars, be reset back to 100. If you manage to destroy all of the Joker's cars on this stage, the text "5000 POINT BONUS FOR GETTING ALL THE JOKER'S CARS" will appear on the screen just before the Batmobile reaches the roadblock at the end of it, even if you fail to destroy one after it appears; once the Batmobile has reached the roadblock, Batman will proceed onward to the sixth stage.
Note: If the Batmobile is hit by a bomb dropped or missile fired by one of the Joker's cars when Batman is down to the last hit of his last life, it will cost him the game; although the bombs can only be avoided, the missiles can be destroyed by one of the Batmobile's own shots for 500 extra points each.