Revealing mistake: During the scene when Hawkins is in the jousting tournament, Griswald takes a swing with his mace and apparently smashes Hawkins' head (inside his helmet) off. Then the horse Hawkins was riding stops, and he extends his head from inside his suit of armor and smiles. Watch carefully throughout this shot - Hawkins' hair/the back of his head can be seen past the edge of the armor where the hole for his neck should be.
Revealing mistake: When Hawkins swings on a vine between windows on the side of the castle, watch carefully. These are all just reversed views of the same shot.
Revealing mistake: During the "Outfox the Fox" number when Hawkins "cuts" the copies of himself in half, the copies are obviously all grown men, which then obviously become little people standing on each others' shoulders; it's easy to tell where the cloak hems of the little people on top end. (00:09:00)
