Other mistake: When the NASCAR pit crew starts working on Herbie at the barn, they initially pull a bunch of parts and tools from their racetrack trailer. One man is carrying a distinctive VW-only wheel rim, which would definitely not fit their regular NASCAR car. The decision to race Herbie had just been made, so they would not have been carrying VW spare parts yet. Nor could they have pulled one of Herbie's wheels yet since they were still carrying the jack to the barn.
Continuity mistake: During the Nascar race, Maggie passes the 48 (Lowe's) car twice in the same sequence. Only the front corner of the Lowe's car is visible when she passes it the first time. Then the shot cuts to her dad praising her on the walkie-talkie. When the shot cuts back to Maggie racing, the Lowe's car is passed again.
Continuity mistake: In the scene when Lindsay left Herbie to race in Trip's car, Herbie is shown to have a piece of clear material on his back revealing his engine. In most other shots, he doesn't have this. This is especially noticeable when he is being put into the garage, after the car crash he was put through to destroy him.
Continuity mistake: Herbie is seen from the back as Matt Dillon beats on the hood and right front fender using a tire iron. When the camera angle pans to the front, there is not even a scratch in the paint, let alone a dent. Herbie's "magic" apparently didn't prevent sheet metal damage as seen in several after-race views.
Revealing mistake: When Herbie is being pulled from the truck at Crazy Dave's, Herbie goes into reverse and the camera does a closeup shot of one of the rear wheels reversing. If you look carefully, you can see an extra set of small wheels behind the tyre which are obviously propping the car up enough so that the cars proper wheels will only skid and not get any traction.
Deliberate mistake: In the end of the NASCAR race, Tripp and Gordon get into a crash making Gordon spin, but he somehow is still able to come in second place even though every other racer was right on his back when he spun. He wouldn't have been able to regain that much speed in that short amount of time.
Continuity mistake: When Herbie is looking at the new yellow Volkswagen, his windshield fogs up. Then a clear spot shaped like a heart appears in the middle of his windshield. But then when it switches to the shot of him moving over to the yellow bug, the heart is at the very right of his windshield (from our view.).