Revealing mistake: Before Paxton is hit with the 3 prong instrument, you can see the bloody holes already on his shirt. (01:01:20)
Continuity mistake: In the scene with Paxton being tortured, when the German takes the ball out of Paxton's mouth, when the ball falls to the ground, the straps form a circle. Right before the German slips on the ball when he charges at Paxton with the Chainsaw, the straps are perfectly straight, 180 degrees. (01:04:05 - 01:04:40)
Revealing mistake: Very obvious that Kana has a rubber prop and eye attached to her face. Especially when Paxton is getting ready to cut her eye off. (01:18:15)
Continuity mistake: When Svetlana is seen falling to the ground after being hit by the car, there is blood on her forehead. When she is shown dead with blood pooling under her, there is no blood or wound on her forehead. (01:21:10)
Character mistake: When the main character follows the Dutch businessman down the stairs (the same scene the girl with the white jacket and white bag walks downstairs before we see her walking up the stairs) there is a commercial which reads "JETZT AUCH AM DVD" which is wrong and should be "JETZT AUCH AUF DVD." (01:22:45)
Continuity mistake: When Kana starts walking towards the train, the clock reads 12:53. As Paxton is leaving on the other train it reads 6:15. (01:25:10 - 01:25:50)
Revealing mistake: Right after Kana opts for suicide by train, watch the security guard who starts running second from the left. He is having a hard time keeping a straight face and is obviously trying to hold off his laughter. (01:25:30)
Continuity mistake: At the end when the man has his throat slit, there is a shot showing his hand by his glasses. In the long shot, his hand is further away. (01:26:10)
Continuity mistake: In the end scene in the train station, Paxton is tailing the Dutch businessman to the toilet. As he turns to go down the flight of stairs, there is a girl in a white jacket and blue jeans carrying a white bag and going downstairs behind the Dutchman. As the scene continues two seconds later, further down the stairs from the opposite angle, we see the same girl magically appear walking in the opposite direction going up the stairs. (01:26:55)
Continuity mistake: When Paxton & Kana escape the factory by stealing a car, he checks his rear-view mirror to see the car pursuing him - the road has a dividing dashed white line on it. When the angle changes to see them driving away from the camera, there is no line on the road. Approx. time code 1:20:00.
Factual error: At the beginning of the movie, the main characters are supposedly in Amsterdam, but everyone is speaking German, it's not just the main characters doing this.
Continuity mistake: When the main character has his fingers cut off with the chainsaw, you can see that three fingers (pinky, ring and middle) get cut off. But in the next shot when you see his hand, and for the rest of the movie, he is only missing two fingers - his pinky and ring finger.
Continuity mistake: At the end of the movie when the guy's head is in the toilet, blood is spilling out into the water. When the shot changes to an overhead shot of the body, the water has no blood in it.
Factual error: In the beginning, the Amsterdam redlight district is shown. They have shown windows on which sex scene shadows appear. Actually, all redlight windows in Amsterdam have big red-colored thick curtains which are closed when any customer gets in with the prostitute. There is no way that shadows can appear and visitors can see it from outside. Doors are also closed from inside, so it is not possible to open it as shown in the film.
Factual error: When Paxton arrives at the station at the end of the movie he is supposed to be in Germany, yet there is a sign on the platform which reads 'Praha'. Also watch out for posters and signs in bad german language like an add which reads 'Neu am DVD' (should be 'Neu auf DVD') and a sign with 'Dieser Bahnhof wird Video - bewacht' ('Dieser Bahnhof wird videoüberwacht') on it.
Plot hole: In the nightclub scene where Josh is drugged before his is taken to the torture factory, Paxton is drugged too. That means he was supposed to be taken there as well, but he ends up locked in a storage closet for the rest of the night. The two girls working for the Hostel pointed out where the bathroom was for Paxton, so they would have known where he generally was. Hard to believe that they or anyone in cahoots would not try to look for him.
Audio problem: When the main character is talking to the American businessman near the end of the movie, when the businessman says "I mean did you do it real slow?" you can tell that his mouth does not match the words he is saying.
Factual error: When the girl has her eye cut off, pus begins to pour out, but realistically there is no reason for this to happen. Pus is only present where infection has set in, and the wound literally just happened moments before, medically it's not possible for any infection to have begun.
Revealing mistake: When the lead character has his fingers cut off, you can tell the hand is just a prop, as it is completely motionless during the shot.
Answer: This is actually a reference to both Eli Roth and Quentin Tarantino's experience with the same hooker. After both Tarantino and Roth "had" the same call girl without either of them knowing, the hooker replied to both of them as she left their separate rooms, "I get a lot of money for you, and that makes you MY bitch. Hence, the opening line for the trailer. Both of them had a big laugh during the premiere.