Frankie Muniz (Corey) was a child actor himself, having starred in "Malcolm in the Middle" (2000).
Rainn Wilson guests stars in this episode, playing himself. Wilson is best known for playing the character of Dwight Schrute in the American version of The Office (2005), a show which utilised and helped popularise the mockumentary format which is used in this episode.
Nathan Fillion and Doug Savant co-starred in "Desperate Housewives" (2004). Doug Savant also had a guest role in an episode of "Firefly" (2002), in which Nathan Fillion starred.
It's not accurate that psychopaths have difficulty charming people--Ted Bundy, perhaps one of the most well-known psychopaths, often charmed victims into coming to his car, for example, and many others (including Dahmer, Gacy, etc.) charmed victims into their homes. While psychopaths do have difficulty actually experiencing empathy for other people, they are usually quite skilled at faking it (most psychopaths realize there is something different about their behavior very young and learn to mimic normal emotional responses). Like many other shows, this episode clearly falls into the trap of assuming killers are easy to spot because they must behave very differently to other people.
The lowest rated episode of the entire series by IMDb users.