Goofs

When the Man in Black knocks Fezzik out and is rolling him over, there's a large rock in the way. At the end of the shot, the rock has moved over to allow room for Fezzik's head.

Westley's mustache changes throughout the film, sometimes it is uneven, sometimes it's longer on the sides than at other times.

After Buttercup pushes Westley down the hill, she throws herself down after him. Towards the bottom, her sash falls off and she's left laying on the ground. However, when Westley goes to speak to her, she is wearing the sash around her waist once more.

When Fezzik and the others storm the castle, camera shots taken from their perspective, i.e, looking toward the mob and castle beyond, the castle's gates are securely shut. However, the shots of Fezzik from the defender's perspective are taken through the wide open gates.

In the sword fight between the Man in Black and Inigo, when the Man in Black throws his sword down and then proceeds into his flip from the "horizontal bar" onto the ground level, he lands a good five feet from the thrown sword. In the next cut, he reaches a foot away to grab the sword's handle.

Vizzini mentions Australia's convict colonies during the movie. This may seem anachronistic since the movie has a medieval setting, but this story is fantasy not history. In fact, its being told as a fairy tale from a grandfather to his grandson. In the novel, this was just one of many (intentionally contradictory) clues about when the story takes place.

Prince Humperdinck correctly identifies the iocane powder after smelling it, even though the Man in Black had earlier described iocane as "odorless". However, the fact that it is odorless is likely why he "bets his life on it" to be iocane powder.

When Inigo, Vizzini, and Fezzik kidnap Buttercup in the woods, Inigo looks like a cardboard cut-out, but in fact can be seen to blink. He's apparently just standing very still.

During the battle of wits, Buttercup's hair can be seen on and off her neck between shots. However, she could have easily flipped it.

When Inigo is explaining why he is looking for a six-fingered man, he explains the man had his father make the sword he is holding but then returned to get it and demanded it be sold for one-tenth the price. If he came to get the sword, Inigo should not have it in his possession. Inigo explains that he took the sword his dad made and attempted to use it to kill Count Rugen. After losing the fight, Count Rugen simply took off leaving Inigo with the sword which is why he still has it.

When Fezzik leans Westley on the castle wall, the wall moves.

Princess Buttercup's dress doesn't have scorch marks after it is burned in the Fireswamp.

Obvious stunt performers (one with a mustache) when Buttercup pushes Westley down the hill, and then follows him down.

When Inigo meets Count Rugen for the first time, it is just after Humperdinck and Buttercup's wedding, which is at night. Yet a window behind Count Rugen clearly shows it to be day.

When duelling, Inigo and the Man In Black sometimes have two shadows.

When Buttercup is talking to the Man in Black on the hill, some obviously modern houses are visible in the valley behind her.

While the Man in Black is on Fezzik's back during their fight, one of Fezzik's lines is heard while his lips aren't moving at all.

On the castle wall, Inigo says "I'll say" without moving his lips.

When the Albino is first introduced, he coughs, but his lips are moving as though he's still talking.

When Westley is fighting the ROUS, you can see a techie by the tree step in and out of the picture.

During the fight with the ROUS in the fire swamp, when the ROUS attacks Buttercup and bites her dress, you can see the silhouette of a crew member's hand holding the dress in the ROUS's teeth.

When Westley is fighting the ROUS, he punches one in the head and then you see the ROUS's hands pull the headpiece back on and straighten.

Clear landing pad in the first fight scene when they jump off the rock. The landing is elevated and one can see the rubber mat ripple as they land. The pad can also be seen when Inigo and Fezzik walk to the edge to look down at Westley climbing up.

When Westley is wrestling the R.O.U.S. in the fire swamp, the tube which shoots the blast of fire is clearly visible just before the R.O.U.S. is set ablaze.

When Inigo hears Westley's cry of anguish (when the latter is subjected to the highest level in The Machine by Humperdinck), he explains that he knows the cry was made by the Man in Black, because the latter's true love is marrying someone else later that day. But Inigo has no way to know that Buttercup is the Man in Black's "true love".

When Westley and Vizzini have the Battle of Wits, Vizzini uses the correct term "Goblets" for the pewter vessels that contain the wine and Iocaine powder every time, except for the very last time before they drink, when he calls them "Glasses".

(At around 30mins) After Vizzini accepts the man in black's request for a battle of wits, he sheathes his dagger. There is nothing stopping the man in black from killing Vizzini during the entirety of the battle of wits.