Character mistake: When Neal tells Rebecca about an Indian Idol and describes the idol to her, she tells him it's the Hindu Idol of Seeta, the goddess of wealth. Actually the idol is of Goddess Laxmi.
Character mistake: When the private investigator shows Castle and Beckett the VIP Liaisons website, "Liaison" is misspelled "Liason." (00:17:40)
Character mistake: When April goes to see Hank at his motel, he states her romantic feelings for him are a result of "Nightingale Syndrome," however, the Nightingale Effect is caused by the caregiver developing romantic feelings for the patient, not the other way around.
Character mistake: The note Six hands the "access man" misspells the word "receipt" as "reciept." He's supposedly a "think tank" genius, so really should be able to spell better than that. (00:27:30)
Character mistake: Steffan addresses his brother, Daemon, as "Steffan" at The Grill after Ellina talks to Steffan about the crystal that plagues Bonnie with nightmares about Emily. (00:15:06)
Suggested correction: You missed the point of the scene. They were imitating each other. Stefan was pretending to speak as Damon. Damon replies with "I don't, Damon" and then "you're really hard to imitate".