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: 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.