During the famous sewer driving scene, in the original, you can see one of the Minis swerving up the sides of the tunnel. Apparently, during testing, Remy J. managed to get one to loop the loop, but only the one time!
As for the fast cars that were destroyed by the Mafia, there's some mystery there. Apparently there is an Aston ragtop, as well as a Jag ragtop, still running around England with those registration numbers. And, if you can bear watching that scene again, there doesn't seem to be a hideous amount of damage done to those two cars (the Jag coupe is another matter). Supposedly those two cars were repaired and sold on.
Another oddity-when the Aston gets thrown off the cliff, the hood (bonnet) opens the wrong way around.
-William