Character mistake: Morgan asks Reid what track on the CD (Some Kind of Monster by Metallica) would help an insomniac sleep. Reid replies with "Enter Sandman" however, Some Kind of Monster doesn't feature the song Enter Sandman. (00:29:00)
Suggested correction: Morgan doesn't ask what song on that album would speak to an insomniac, he asks what Metallica song in general would. He says, and I quote, "Okay, so I'm an insomniac who listens to Metallica to get to sleep. What song could possibly speak to me?" His query is in regards to the band's discography as a whole; neither he nor Reid mention a specific album, so the fact that "Some Kind of Monster" is the CD that they find is, ultimately, irrelevant.
The team was looking for what CD Slessman listened to the most to figure out what his password could be. They had no luck going through all his metal collection. The clue was suppose to be Slessman listened to "Some Kind of Monster" CD the most to help him sleep, which is why it wasn't in the case.
Character mistake: Close to the end of the episode, Dr. Reid says to the psychotic guy that was holding hostages, "M-theory cannot be proved." It should be "proven, " not "proved." Dr. Reid is supposed to be a genius, so he should be the last one to make such a mistake.
A Real Rain - S1-E17
Character mistake: In the initial meeting at FBI headquarters, the agents mention the Zodiac killer. Gideon says about him "Yeah, and he killed for 30 years without being caught." In actuality, the Zodiac's known victims were killed between 1966 and 1970. In letters to the public, Zodiac claimed responsibility for several other murders (most of which were solved without being attributed to Zodiac), but no later than 1974. Gideon's statement was off by at least 22 years.
Character mistake: In the meeting room, there's a clear spelling mistake of "Manditory" in bold letters on the whiteboard behind Gideon. Flashes up there several times during the scene. (00:16:00)
Character mistake: In the scene where the agents are called to the conference room and start talking about the case, the camera pans the room and shows a white board with information written on it. At the top of the board, in bold letters and asterisks around it, is the word MANDITORY.
Character mistake: Derek Morgan says that he discovered the body of a dead boy in 1991 when he was 15 years old. Later on, you see Garcia searching the computer for personal info on Derek Morgan. According to the computer; Derek Morgan was born in 1973 which would make him 18 years old in 1991, not 15.
Character mistake: In this episode the unsub is copying the murders of Jack the Ripper (with men as victims). The Unsub also taunts the police and BAU with letters, even using the Dear Boss salutation. The BAU draw upon the Dear Boss letters from the original Ripper case as part of their profiling - not only of the unsub but also the Ripper. Handwriting comparisons has shown that the author of the Dear Boss letters was most likely a journalist and not the Ripper. Whilst the unsub may have been ignorant of the forgery status of the dear boss letters, you would expect the BAU to be wiser.
Character mistake: Dr. Reid calls Penelope "Kristy" on a phone call.
Suggested correction: He calls her "Garcia."
Character mistake: At the end of the episode, Rossi quotes Anne of Green Gables author Lucy Maud Montgomery, but accidentally calls her "Lucille".
Character mistake: When Emily Prentiss makes note of the 110 V outlet having no GFI, she calls it 'Ground Fault Insulation', when in actual fact, GFI stands for 'Ground Fault Interrupter'. (00:11:00 - 00:12:00)
Character mistake: When Morgan looks up Charlie Luvet's car GPS map history, the last address reads "11257 Palmdale Drive," but when Morgan phones Hotchner with the address he says, "11257 Palm Drive."
Character mistake: When Reid is visiting his mother, playing Scrabble, he has eight tiles on his rack (ROLOAWAD), but a player can only have seven tiles at a time.
Mosley Lane - S5-E16
Character mistake: Reid tells Mrs. Hillridge that he's been working for the BAU about five and a half years, which is roughly since the pilot aired in 2005. But flashbacks in "Tabula Rasa" show that Reid was a relatively new rookie in 2004, which is roughly six years. Considering Reid has an eidetic memory, the six-month discrepancy is a bit suspicious.
Character mistake: When Reid and Rossi propose the theory that Kate knew Syd and Jimmy before her disappearance, and JJ expresses her skepticism, Rossi retorts "they're handsome, charming, 19." But while reviewing the case on the flight to Maryland, JJ mentions that the boys are both 20.
What Happens at Home... - S6-E10
Character mistake: After the murder that takes place while the team is at the church meeting, they gather together to talk about narrowing down the suspect list to the people who didn't show up to the meeting. Spencer shows up with a stack of papers and says 18 suspects didn't show up. We then see his actor break character and almost laughs when he looks over at Ashley, whose actress too almost breaks character from laughing.
Character mistake: Unsub calls his victim Marcy, her real name, as opposed to Rose who he believes she is.
There's No Place Like Home - S7-E7
Character mistake: When Travis James' juvenile record is brought up, Oklahoma is spelled "Oaklahoma."
There's No Place Like Home - S7-E7
Character mistake: On Travis James' arrest report it shows his DOB as 10/28/98 and Garcia says he is 22. This show is based in 2011 at this point so the DOB should be 10/28/89.
God Complex - S8-E4
Character mistake: Spencer says that leg transplants are medically impossible, however, there was at least one documented successful double transplant performed a year before the season aired.