Y'all, I'm going to keep this short and sweet.
"Familiar" is a spooky, Stephen-King-esque episode. A small New England town in witch-burning country, a couple dead children, an ongoing affair, and a scorned wife summoning the powers of the hell. Nothing to see here!
The witch's "familiar", a large, black dog or hellhound, appears to the town's small children as their favorite characters, luring them into the woods to their gruesome deaths.
Mulder, being Mulder, immediately jumps to witchcraft, given the town's sordid history of witch burning, while Scully is predictably skeptical. As they investigate the case, they uncover the small town's darker side — the mother of the first murdered child was having an affair with the police chief. When the police chief's wife figures it out, she goes colonial, enacting revenge by way of a witch's curse.
Unfortunately, the familiar is not particular about its victims. When it lures the woman's own daughter to the woods to meet a similar fate, she realizes she's bitten off more than she can chew. Even as she spontaneously bursts into flames with the tome in her hands, she claims she can reverse the damage.
The book, predictably, is unharmed.
But never mind witches; the beloved television characters are easily the scariest part of this episode. Mr. Chuckleteeth? Bibbletiggles? What parent in their right mind would let a three-year-old watch those things? They're the stuff of nightmares.
The episode doesn't break new ground. It's a standard monster of the week, reminiscent of "Chinga"; there's not much emotional depth, it doesn't leave us thinking, and it exists primarily to scare the pants off us. Mr. Chuckleteeth and his hideous jingle does a pretty good job of that.
Mulder does call Scully his "homie", so that was pretty amusing.
"Familiar" made for an enjoyable hour of TV, even if it didn't have the depth I would have expected for an episode about murdered children. Given the setting, the characters, and the premise, it has all the hallmarks of an old-school X-Files episode.