Omg that is the best idea ever!This never occurred to me while I was watching the episode, but could the spool itself be one of the keys? It'd be an interesting twist if the keys weren't actually keys, and the spool does look like it could fit one of the keyholes.
Well okay not the best idea in the history of forever but that is a really good idea or theory one that I know really want to see happen.
The spool itself is being used to foreshadow something so it does seem possible that it could be one of the keys.
Also like all Rarity episodes this was a fantastic episode.
I really enjoyed the character of Rarity in this episode as she was written really well and that when she is at her worst you can see how she got there and that she is still a good pony.
I also enjoyed the song and its reprise as Rarity has great songs as usual.
Lastly I also really enjoyed the ending of the episode and the mane 5 making up with Rarity, the befriending of the assistant and Rarity's diary entry as well as seeing Rarity learn her lesson was all really nice to see.
Also the animation like the rest of this season is pretty good.
So all and all another great episode from a great season and is going into my favorites along Flight to the Finish and if the season keeps up like this it might replace 2 as my favorite.