Corrected entry: After Albert is thrown through the window, there is a large bloody gash over his right eyebrow. The next day, there's no gash or scar there.
Corrected entry: In the scene where Seth McFarlane is learning to shoot, he fires 8 shots when the gun is a 6 shooter.
Correction: The first time, with the cans, he shoots 5 times and they reload, then he shoots 6 times. Then it cuts to the bottles where he shoots 6 times. The scene then cuts to shooting the plates, where he shoots twice, and while we don't see him reload, we also don't see the "set up" so there was plenty of time off camera for them to reload, this also becomes part of a target practice montage where we only see the shooting.
Corrected entry: When Albert has his hallucination dream from the Indian drugs, he sees and hears Anna tell Louise the line "How can you be blind with eyes that big?" and Louise responds back "They're not that big!" and turns around with digitally enlarged eyes. This was showing it as a memory that Albert had of the girls' conversation earlier in the movie. However, when that conversation happened, Albert had already left the party and was not around to hear those lines spoken, so he could not have dreamed about it.
Correction: Like you said, it's an hallucination, he is having not a flash back dream. In the same scene he gets chased by a group of dwarf cowboys, one of which shoots him through the heart. Obviously this didn't happen either because he's not dead. That scene is mainly an excuse to make gags that are physically impossible in real life.
Corrected entry: At the party scene where Anna lifts up her dress to show Albert the metal cage underneath, later on they have left the party they are both on the horse, however it would be impossible for Anna to sit on the horse with the way the cage was shaped and the length of it - it would have been visible.
Correction: Before leaving the party, she removed the cage. At another scene in the party, you can tell she is not wearing it.
Corrected entry: In the scene where Liam Neeson is chasing Seth McFarlane, there are four gunmen (including Neeson) before McFarlane crosses the path of the train. After he crosses the path of the train, there are five gunmen.
Correction: The shot with more "gunmen" actually is an angle where Seth is leading the group of gunmen.
Correction: In the scene following the lead character's head getting cut, time has passed. His friend greets him at the door and says along the lines of "It's been, like, two weeks... What have you been doing?"