Fan theories for Frozen seemed to dry up a few years ago. Everyone has since moved on to Moana and Coco, replacing "Let it Go" with new and delightful songs that will eventually bore into the world's collective consciousness until everyone hates them and/or the new Disney movie comes out. No one wants to hear new interpretations of a movie that came out in the pre-apocalypse of 2013. Besides, everyone's heard that Tarzan/Little Mermaid/Tangled connection theory by now, so what else is there to discuss?
There is one thing that we haven't really discussed up until this point: That weird dungeon. What's up with that place, anyway?
That a castle has a place to lock away prisoners isn't notable by itself, but this is Elsa we're talking about. She created a whole ice castle in minutes, complete with what we hope is a functional sewage system. If it were any other dungeon, Elsa would have no problem busting out. But there's one problem: The shackles that cover her hands. Like the gloves she used to wear, these iron mittens keep Elsa's powers in check (at least, for a whlie).
But wait... Hans is the one who schemes to lock Elsa away, and presumably his goons are the ones that put the cuffs on her. How would Hans know how to suppress Elsa's powers and keep her in check? Doesn't it seem a little convienent that a dungeon (and special restraints) capable of imprisoning an omega-level ice sorceress just so happens to be on the castle grounds? Who would have implemented such a precaution? When you think about it, there's only two people that could have had this foresight: Elsa and Anna's parents.
It fits. Before dying on their ill-fated booze cruise, the former king and queen of Arendelle displayed a shocking capacity for cruelty. They locked Elsa away for years, teaching her to shove her feelings deep down inside and never let anyone inside -- not even into her room.
Mom and dad were paranoid enough to inflict deep psychological scars on their daughter in the name of "safety," so it seems more than a little likely that they would have a backup plan in case Elsa gets out of control (or maybe just wants to go outside like a human being). Those iron mitten shackles seem like they were made for Elsa because that's exactly what happened, at the behest of her fearful and frankly terrible parents. A scene explaining all this was likely never even considered, probably because it's hard to make catchy song lyrics about child abuse dungeons.