Revealing mistake: While escaping from the orgy raid, Valeria stops and kills a few pursuers. However, her last strike never makes contact with the guard.
Revealing mistake: When Conan cuts his way through the orgy we first see him cut a man in his stomach region - the bag of blood hidden under his clothes. Conan then cuts another man in the neck, but blood doesn't begin to flow until that man reaches up to his neck, making it rather obvious that he has his bag of blood in his hand.
Revealing mistake: Before the crucifixion scene of Conan, Thulsa tells one of the women on the cliff, "Come to me child," so they would jump off. If you watch closely you'll see, right before she hits, the pad she lands on before the angle changes. In the next shot, they then show her lying through broken wood flooring.
Revealing mistake: Obviously there are no planes in the world of Conan, yet a jetplane vapor trail can be seen in the sky above Conan's head in the "tree of woe" crucifiction scene. The exact shot when this is seen is when the camera is pointing upwards at him from the ground.
Revealing mistake: Several times throughout the movie you can see that some actors have contact lenses in their eyes. Obviously, there were no contact lenses during the Hyperborian Age. I don't mean the intended effects created with the contact lenses - for example, green eyes - I mean that you can see the actual lenses. You can see the circles outside the outer circumference of the iris, as is usual for soft lenses.
Revealing mistake: After Conan pushes the heavy cauldron to spill the green liquid, the cauldron falls off and bounces like a football, revealing it's a prop.
Revealing mistake: When Conan kills the baddies in the orgy, he aims a blow at a man's neck, then punches a guy standing next to a column (and later stabs his stomach), but his punch misses by far.
Revealing mistake: When the movie begins and Conan's father is talking, watch the pattern of the blue-screened clouds behind. The same clip is being repeated over and over again.
![Conan the Barbarian mistake picture](/images/screenshots/305000-305999/305239_sm.jpg)
Revealing mistake: When Conan is fighting in the ring and smashes a guy's body against some [prop] rocks, the painting cracks and falls off.
Revealing mistake: When the dogs are eating Conan's dad, he is replaced by an obvious stuntman with a noticeable wig.
Answer: Like an Army Drill Sargent, he was berating them for not doing it better. Toughening them to become the best they could be.
Also, the other student laughs at Conan's punishment, so the teacher kicks him to teach him some humility.