Continuity mistake: The tow truck and the red van it's towing change positions at the alley's entrance between shots. (00:01:00 - 00:23:35)
Other mistake: Nick pronounces the plastic surgeon's name as "Yergen" in one scene and as "Jergen" in the next. At the end, she becomes Dr. "Yergen" again. (00:29:40 - 00:31:10)
Near Death - S2-E23
Plot hole: Dr. Linsman puts a heart monitor on Nick for the experiment, but for some bizarre reason, never questions why her "patient" has a resting heart rate of only one beat every ten minutes.
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)
Close Call - S2-E25
Continuity mistake: Though the camera angle doesn't change, the brightly lit Chinese-character sign on the wall outside the window moves several feet to the right between takes. (00:09:10)
Crazy Love - S2-E26
Continuity mistake: The flashbacks here contradict series canon. Nick's victim, Amaya, is shown to have been bitten (by him) several times. In every other instance, unless he had multiple captive ladies to "sip" from, Nick's bite was fatal in one go. In fact, it was a major recurring plot point that Nick "couldn't stop."
Partners of the Month - S2-E18
Continuity mistake: Schanke's mother-in-law had previously been established as dead, yet Schanke's talking to her on the phone in this episode. (00:16:25)
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)
Factual error: Nick's '62 Cadillac had an attached police radio, but never had a car phone, nor the giant external antenna attachment they required in the early 90s. Yet Schanke somehow makes a call from Nick's "car phone" in this episode.
Father's Day - S2-E7
Continuity mistake: The godfather's thugs storm Nick's loft and riddle him with bullets. We actually see the bullets coming out of his back, leaving holes in the back of the vest he wears. But when the "vamped out" Nick turns around to face the camera, there are no bullet holes in the front of his vest. (00:23:20)
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.