Revealing mistake: When LaCroix opens the box containing Divia's little "surprise," the severed head's eyes move slightly as the covering tissue paper is removed. (00:07:20)
The Games Vampires Play - S3-E15
Factual error: At the end, Nick recites the "you have the right to remain silent" spiel to Rita as he arrests her. Suspects in Canada, where this show is set, are not "read their rights." That's a U.S. law (the Miranda Act) and it isn't observed north of the border. (00:41:45)
Revealing mistake: When Robert is shot, the car blowing up in the alley is sort of half an explosion, abruptly curtailed. Severely cold weather during shooting literally froze the cameras and left only a few seconds of usable footage. That snippet is repeated for effect, but the explosion still looks "cut off" because it is. (00:32:00)
Visible crew/equipment: When Natalie is telling the amnesia-stricken Nick that he's a vampire, an equipment shadow moves across the stove in the lower right hand corner of the screen. (00:35:15)
Continuity mistake: The clock on Natalie's lab wall jumps forward almost half an hour during a 2-minute conversation with Nick. (00:27:25 - 00:29:05)
Plot hole: Throughout the first two seasons, Nick was always able to sense other vampires and to instantly differentiate between vampires and humans. Here, he inexplicably fails to detect that the returned Janette is now mortal. She has to tell him. (00:27:10)
Factual error: The costumes in the flashback to Nick's wedding are a mishmash of the mismatched, coming from several different eras, including a full metal suit of armor that's at least 2 centuries ahead of the flashback's period setting in the 1200s. (00:14:00)
Plot hole: Because he has no discernible vital signs, the wounded Nick is declared dead in the hospital. When he revives, he's rushed into surgery, where he'd surely have been reattached to a monitor. Somehow, though, no one on the medical staff notices that their patient still has no normal pulse or heartbeat. (00:05:05)
Answer: Nick was sick and tired of being an immortal bloodsucker. He wanted to be human, fall in love, get married, have children, grow old and die. As for Janette, according to her, she fell in love and the passion she felt "cured" her of her blood lust.