Congrats on your first jam! It's a big accomplishment, so definitely enjoy what you've put together :)
The idea of playing as two characters in a puzzler that requires both to complete the level is perhaps a little predictable for the theme but was executed very well! Plus, there's nothing wrong with doing something a little more straightforward, especially for your first jam where you should probably focus more on execution than unique concepts. My very favorite part of your design is the fact that abilities are locked away inside boxes that you pick up in the levels. I find that to be quite clever and unique. That idea alone bumped up my rating for your design by 1 star (won't give away final rating, but just know I think it's very well done).
The presentation of the game is also expertly done. The font, especially the title, is really cute and captures the essence of the characters really well. The characters themselves are incredibly adorable. The colors are pleasant. I really just love the design of the characters, and I appreciate the extra touch of having player 2 have a sad/worried mouth as opposed to the happy player 1. It would've been easy to just recolor them and keep them identical, but that extra touch and attention to detail is sometimes what takes a mediocre game from a jam and gives it the necessary charm and love that it needs to make it great. And I definitely don't think that the game is mediocre.
The puzzles themselves were fun and at least a little challenging when suddenly one character couldn't move or jump. The music is really chill and definitely fits the aesthetic of the game. I will say that at one point the music completely stopped for me, which unfortunately made the game feel a lot more lifeless. Had to restart to get it working again. I will note that I do wish there were more sound effects. For example sound effects for jumping, pushing, landing on the other character, and ability boxes falling would have really increased the feel and enjoyment of performing those actions.
I also feel like this game could've gotten away with a bit more flexible characters. Stretch and squash would really add to their characterization. When they jump make them stretch quite a bit more, landing from a high fall should make them look short and fat as their jelly-like bodies adjust to the movement. If player 1 stands on player 2, a similar short and fat look could occur and maybe have the player look like they have a headache as they look up at the player on their head haha
Oh and unless I'm mistaken, there's no button for quitting the game/exiting to the menu. That would be a nice addition.
Of course, just like everyone else's games, there's only so much that can be added in 2 days and I'm sure there were things that got cut. But these little touches would have really been awesome to see! :)
I'd love to see this game updated after the judging is over, if nothing else then at least to fix the music. You've got a really neat game here! Again, good job and congrats!