Labyrinth/Fridge

Fridge Brilliance

 * Sarah's real mother (as seen in gossip rags) was dating an actor, which is a photograph of David Bowie. Since the entire film, of course the Goblin King would resemble someone dating her mother! The Novelization is more blunt about this, as it goes further into Sarah's backstory via a Flash Back or two.
 * Ambrosius is another name for Merlin.

Fridge Horror

 * In Labyrinth when Sarah has her memories wiped, she is taken care of by a garbage hag, who wears a ton of garbage on her back. When she insists that everything that Sarah truly loves or needs are her toys and mementos, she piles them on Sarah's back, much like her own mountain of junk. This implies that she is trying to turn Sarah into another garbage hag, which in turn implies that the garbage hag might be another girl who failed to rescue her brother from Jareth. To make matters worse, you see that there are at least half a dozen others in the background, maybe more. Indeed, there may be hundreds or thousands, since when Sarah first ran into the garbage hag, she mistook her for another heap of junk because she was lying there doing nothing.
 * There's also the strong possibility that every single goblin in the Labyrinth (with the possible exception of the goblin king, himself) was once
 * What about the Bog of Eternal Stench? Supposedly, if you come in contact with its mud or water, you smell bad forever. While not addressed any further than that within the context of the movie, this presumably means a lifetime of rejection and loneliness until you're driven to madness or suicide. Or you become sort of a "bog monster" (not necessarily physically deformed, but people might call you that) who tries to trick or force people into the bog in an attempt to create companions (although Sir Diddymus seems pretty friendly, and he claims not to smell the bog).
 * In the official tie-in sequel manga, that's answered. Remember how ? Well, he did.   Apparently it's not exactly a blast.
 * Actually, Jareth tells Hoggle he'd turn him into a  when Hoggle responds with an incredulous 'Really?'