Nice job with all your hard work for the jam! Here's my in-depth review:
Design [2/5]: I'll start with the positives: the concept of controlling one character at a time to get a princess through an exit door makes for a very nice puzzle game ripe with opportunity. I think you have a nice cast of characters that are all creative and unique.
Having said all of that, I thought the execution was weak and the level design is incredibly frustrating. It is possible to get completely stuck on the very first level if the Knight falls into that first pit (happened to me). At first, I realized I could no longer collect the coin at the bottom left of the screen, but that frustration turned into a huge eye-roll when I realized I also could no longer finish the level. To make matters worse, there's no obvious way to restart the level, so I just had to refresh the browser page and start the game over. In general, I think the level design is incredibly frustrating, and the fact that there's no way to restart the level after making a mistake means that the best players will be punished the hardest for making a mistake (seems backwards to me). If I make it all the way to the last level and make a mistake, I'll have to restart the entire game just to see the ending, which is a poor design choice. It's too easy to become stuck in the middle of a level, and I think that should have been brought into consideration (especially in the earlier levels).
That was my experience when I first played the game, but it wasn't until I came to this comments page and read through some of the other comments that I realized you actually can restart the level. However, you have to open the options menu and click through a couple of buttons to do it. Aside from that being a clunky way to handle restarting (a simple press of the 'r' button on the keyboard would have done just fine), the player is never told about that in the game. There is a tutorial screen, but it mentions nothing about how to restart a level. Since dying or becoming stuck is such a strong possibility, it's really important that players know how to restart the level, so that was a huge problem for me.
I also faced some other minor annoyances while playing. I was frustrated that your character always faces to the right whenever you stop moving, even if you were moving left. This can become a problem for any of the characters with an attack, since attacking left means you have to be moving and attacking at the same time.
Again, I want to say that this game is a nice concept in theory, but I was so frustrated by the level design and the lack of an obvious way to restart the level that I couldn't finish playing it.
Adherence to the Theme [5/5]: You have multiple characters, but you only control one at once. Nice job!
Originality [3/5]: As nice as this game is conceptually, I've seen it before in a game called Thomas Was Alone. I don't want to dock you too much, considering that's a relatively unknown indie game, but the idea of a puzzle platformer with multiple characters that you control one at a time is not completely original.
Overall, I can tell you've put some nice effort into this project. The game looks nice, it's an interesting concept, and it's (mostly) bug-free. Keep working at games and I'm sure you will improve as a developer in time!