I'm not sure if this is actually a slip-up, but when the beeper float goes out of control, Gerald says, "There's an emergency brake underneath the city hall!" But the brake is under the float, not the city hall! There's no way Arnold would outrun the float, go to the basement of the city hall, and find a lever!
What emergency brake under city hall?!? If I remember correctly, Helga's dad put that huge beeper float on top of the one the kids made, it tipped and ripped off. Arnold found a trapdoor of some sort, and went inside the control room.
Remember how Arnold had a ride for each part of the town? Apparently he had something for city hall. The trap door was under that... *sigh* Special people...
Also, when was the emergency brake in the middle of the front of the car? And if it was there, wouldn't Arnold of had to push on the brake? Beccause if you were sitting in the driver's seat, you would grab it and pull back....at least I think so.