The idea of two characters joined together is seen many times, but joining two babies with a sheet of skin is certainly original! The game itself is a nice and fun puzzle platformer with an interesting mechanic that could lead to some very interesting levels. However, the game could use some more polishing. Here are a few suggestions that I think would make the game even better:
First, the level design feels a bit untested. Some parts are very difficult for no apparent reason, it's very demotivating for the player to have two very hard parts in a level, one at the beginning and one at the end. I'd suggest keeping the number of hard parts to one per level. The positioning could also use a bit of rework, sometimes there is empty space on one side but playable platforms on the edge of the screen on the other side. This is also connected to camera movement or rather the lack of it. It would be great if there were walls on the sides to prevent the player from going off-screen.
Next, the art feels a bit inconsistent. The exit doors, characters and syringe spikes all have this cartoony feel which is taken away a little by the single-colour rectangle platforms, buttons and other elements. I suppose, there was not enough time to draw everything.
Finally, the gameplay itself was a bit strange. Limiting some abilities only to one of the characters seems a bit unnecessary, but perhaps I just didn't make it to the levels where this is important. Physics-based movement of the non-controlled character is sometimes very difficult to control, especially in cases where some sort of a swing is needed. Sometimes I felt more like hacking the level than actually solving it.
Overall, really good job on making a game in 48 hours on your own, especially as you also made all the art and audio! I had fun playing your game and I hope my feedback can be useful for you.