Factual error: As the creepy "Nightcrawler," master vampire LaCroix taunts Nick via his CERK radio broadcasts, which Nick listens to on his Cadillac's car radio. Except, CERK's studio sign says it's an FM station. And Nick's Caddy, supposedly a '62, still has its factory radio (we get lots of good close-ups of that), which in 1962 was strictly AM. So how was he receiving LaCroix's station?
Factual error: Though she wore medical smocks and occasionally a baseball cap to hold back her hair, Natalie was never correctly attired when she performed her autopsies. In fact, she usually worked with her hair loose and hanging down over the corpse, which may have made her look prettier, but is a serious breach of forensic etiquette that could contaminate the evidence. Even the best-coiffed coroners still have to wear sterile caps and gear.
Factual error: The police call-radio added on to Nick's old Cadillac (along with a handy dandy detachable dashboard police light and a siren) somehow managed to work for all 3 seasons without an antenna.
Factual error: The Cadillacs (all three of them) used throughout the series to play the part of Nick's sea-green, large-trunk vampire transportation were not, as claimed in the show, 1962 models. Nick's car, in all its incarnations, was actually a '61.
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.