Continuity mistake: There are numerous instances (plenty even within the first fifteen minutes) wherein a character's hair changes from messy or strands hanging down or out to fairly neatly combed - far too many to point out at a particular time in the movie without being tedious and redundant (plus, this isn't necessary to be valid). For example, Mr Anderson's hair changes within a few seconds. There was a wad of hair sticking out on his left side, then it was neatly combed on the left side but the right side was disheveled. Patrick's hair, which is almost always messy, still has noticeable variations (such as dangling strands on one side or in his part) within seconds and/or when the camera changes position. Charlie's hair, in particular his bangs, frequently has gaps that are no longer present the next time he is seen. Given the number of hair continuity errors, they are best documented as one repeated mistake. (00:07:04)
Continuity mistake: The way Charlie's necktie is tied and hanging varies during his first party. Sometimes, it is a little loose around the neck but the knot is tight and askew. Other times, the tie looks like a typical neat one. Interestingly, the tie is mostly loose and crooked at the beginning, but quite neat and typical after he eats the laced brownies (but goes back to loose and tilted). (00:26:08 - 00:28:03)
Deliberate mistake: There are no yellow/amber lights as Patrick drives Sam and Charlie through the tunnel. Yellow/amber lights are present as soon as drivers enter the tunnel - a warning to slow down, as well as help drivers' eyes to adjust to the light level inside. I presume it was better to have all white lights while filming (and traffic was controlled). (00:27:33)
Factual error: Charlie was at Mayview State Hospital typing by the window. In the not-too-far distance, the University of Pittsburgh's Cathedral of Learning is visible. Mayview was located in Bridgeville, PA which is about 15 miles away, so The Cathedral shouldn't be visible. (Pittsburgh's terrain is hilly - not flat enough to see very far). (01:33:40)
Other mistake: When Emma Watson says "get wasted all the time", her British accent is very obvious, especially when she says "all."
Continuity mistake: Towards the end when Charlie is giving a goodbye hug to Sam before she goes to college, the sun changes between shots.
Continuity mistake: When Sam is preparing the milk shake for Charlie, the ice cream scoopfuls inside the blender change shapes from shot to shot.
Factual error: In all of the cafeteria scenes, the food pyramid posters that can be seen on the walls are the updated 2011 versions, not the ones they would have had in 1991 and 1992.
Factual error: Whenever Charlie, Patrick, and Sam go through the tunnel into the city, you can see "Consol Center" on the road sign. The Pittsburgh Consol Center was built in 2008, but this movie's set in the 90s.
Revealing mistake: Right at the end of the film when Sam, Patrick and Charlie are driving through the tunnel, when Charlie begins to stand up on the back of the truck, look slightly beneath his flapping jacket and you can see the safety wires attached to him.
