Other mistake: While asking Napoleon to pull him into town, Kip is putting on his roller blades. They live on a gravel road seen in other shots which would be impossible to rollerblade on while being towed behind a bike.
Other mistake: When Dean compliments Les on the great driving making up for a year of boredom, Les looks around up in the air in a direction away from the car, then suddenly says "there's a scratch on my car." He then looks down on the car at the scratch and shows Dean. He said the "scratch" line before actually seeing it.
Other mistake: When the things clean Mom's dress, the purple goo goes directly onto the couch on the right side of the room. After Conrad asks about the couch, and the camera pans over to the now filthy couch, look at the end table and lamp. They were in the direct line of fire, but didn't get touched. Also, look closely at the lamp. It appears to be a piece of thin lumber cut into a lamp shape.
Other mistake: When Robert Downey Jr. lowers the helicopter onto the freeway to yell at the truck driver, he is very close to the truck driver, so close that the truck driver can even hit the helicopter. Why does a long haired man standing underneath a helicopter not have his hair blown around?
Other mistake: Jack's parents were at a Halloween party when his mother went into labor. Later in the movie when he's asked by his teacher he says his birthday is September 12th.
Suggested correction: The movie doesn't specifically say this is a Halloween party. This may simply be a costume party which can and do happen multiple times a year.
As you stated, it doesn't say it's a Halloween party. In fact, there's signs in the room that say "Beaux-Arts Ball."
Other mistake: Whenever Fozzie is driving the Studebaker, the movements of the car don't correspond to the way he moves the steering wheel (he tends to crank it back and forth a lot).
Other mistake: When Gregory has read the note from Fregly, he realises he put his thumb on a booger. When we see Greg on the floor, the note should be nearby. Instead it is several feet from him, in line with the bin. This is strange as Greg only dropped it and the note didn't flutter over there as Greg only turned when he hit the floor. In fact, the movement should've moved it closer to him. In line with the bin is even weirder.
Other mistake: In Tiffany's converted garage, Tiffany says she's thinking of putting in a ballet bar, but there's one there already right next to the big mirror, where it's supposed to be.
Other mistake: During the pub fight scene, the guy who got hit with the glass cup (Wound on his forehead), pulls a six shooter out of his pants, but he fires eight bullets at Harry's umbrella.
Other mistake: Vic and Stu get into a shoot out inside the animal hospital with some thugs, guns firing all over the place. The building is full of animals like dogs and cats and parrots. However, the animals stay completely calm and quiet during the entire gun fight and seem unaffected by the rapid, very loud banging of gun fire. Even right after it, a cat that just had it's tail stepped on sits on a dead body and meows like nothing happened. This is completely uncharacteristic of how animals would act to loud gunfire in an enclosed building, especially in a vet's. (00:45:00)
Other mistake: In the race scene between Milner and Falfa, you can see exhaust smoke coming from Milner's car, but in a previous scene the station attendant mentioned Milner taking the header plugs off. By taking the header plugs off, his exhaust is running from the headers and you wouldn't see exhaust coming from the tail pipes. (01:03:15)
Other mistake: When Jim Carrey runs out of gas, and takes his what appears to be either a one or two gallon gas can and fills it, the quantity dispensed shows 5.74 gallons.
Other mistake: Duke is running through the city while dragging Max by his leash. A close-up shows Max being pulled between the bars of a metal fence, but the gap is much too small for Duke to have passed through.
Other mistake: In the 'sped' class the teacher starts taking attendance. He goes through and finishes but he never calls the main girl's name or her friend.
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.
Other mistake: In the championship game, the Yankees batter hits a foul ball when they score their winning runs.
Other mistake: In the scene where Rosalee and Tad are talking on the airplane, in the background with the two airplane windows one is white like it's a cloud and the other one is blue like blue sky, and they don't change for the whole talking scene. So it's like they stopped in mid air.
Other mistake: At the beginning, the pirates find about five tickets in the treasure chest - nowhere near enough to admit all the pirates into the theater.
Other mistake: In the cupcake shop, Lucy crushes several cupcakes. These cupcakes have icing on them. But no icing goes on Lucy's hands at all. (00:24:35)
Other mistake: The Russian flag in the Russian commander's office is upside down.