Nice little puzzle platformer. There's a lot of submissions with controlling two characters and swapping between them, but from the ones I've seen, this is one of the best. I really like how different the characters are while still maintaining a balance between them and not making one seem just as a piece of baggage to carry with the other. The attachment mechanic makes for some interesting uses and it was delightful to figure out that it works both ways.
Now there are a couple of things that could be improved to make the game even better. The most noticeable one is not seeing any visual cue as to what character is currently selected. Normally, this would not be much of a problem as the controls would reveal that, but the attachment mechanic made it so it's not obvious which one is active. It would be great if, for example, the inactive one was asleep with its eyes closed or something.
Next, It took me a while to figure out what the goal actually is, the exit particles (especially the blue ones) are quite faint and hard to notice for a new player. Painting the exit similarly to the start would help this.
Finally, and this is a very small detail, the music, even though great, felt a bit repetitive after a while. In a puzzle game such as this, it is expected that the player will spend a fair amount of time scratching their head not really doing anything and it would be great to give them something more diverse to listen to.
Overall, I had fun playing your game, good job on making something like this in such a short time!
PS: Thanks a lot for that "Skip level" button, it makes playing and rating a game jam puzzle submission so much better.