That was there to show that vampires don’t take a holiday just because the vampire slayer is dealing with a personal tragedy. Kind of a grim “life goes on” deal.
This predates TV, but the stories by William Hope Hodgson about Carnacki the Ghost-Finder are set in a world in which the supernatural (specifically, ghosts) exists, but in some of the episodes, the supposed hauntings he investigates turn out to have non-supernatural origins.
Fringe walks close to the line between natural and supernatural. In-universe, there’s a natural explanation for everything, but some make the suspension of disbelief stretch pretty far. There are some episodes that are somewhat plausible extensions of current technology, though.
Which makes sense, seeing as it’s adapted from “The Bet” by Chekov.
As I took it, the point of the vamp attack at the end was that no matter what else happened in her life, even at her lowest points, she was still the Slayer and still had a job to do.
I don’t think there was any supernatural or magic in the Buffy episode “Ted”, was there? The John Ritter look alike was evil, but not supernaturally evil.
If you will recall the breeding mother was a mutant in the sense that she felt no pain, and was IIRC in her 70’s or so while still breeding, and produced these mutant throwback (literally) children with impossible DNA where multiple DNA from several sperm donors, (her mutant sons) was mixed together in a single person.
That was strange enough IMO to be “supernatural”.
Home wiki
How do you say, “Rut-row!” in Russian?
Well, he was a robot. With emotions. Who killed 4 women trying to find the perfect wife.
Yeah, but it’s pushing it into 'terminator" world where robots exist, which is close. Same with Warren’s robot girlfriend episode.
Another Supernatural episode, “Family Remains,” lacked supernatual elements, to the surprise of our heroes. It may have actually been a rip off of the “Home” episode of X-Files referenced in the OP.
Heck, the first episode of the Twilight Zone revealed that all the wacky stuff was simply hallucinated by the subject in a mundane psychology experiment. And don’t forget the episode where a doctor’s birthday party transitions to everyone suddenly wanting in at their neighbor’s bomb shelter…