Just played it through as far as I could get. Really nice premise, though the gameplay is very hard... I don't think I could've made it past the first level if not for Game Maker's built in save/load (F5/F6). I got stuck at the end when I saved
after jumping the ninja off the ledge to the ship. And this was after I had painstakingly walked everyone to the garden, since I thought that was the exit and didn't know there was a ship to the right.
I noticed the collision issues you were talking about, especially with the dragon, and it feels like it is being caused by changing her mask around. To keep objects from getting stuck, it's usually best to keep an object's mask a constant size and square. In general, characters' masks felt a little large, making it hard to do some of the jumping sections. If you want an example of a typical mask size/shape, I provided some sample masks to use in
the dragon's sprite sheet (one for standing and one for crouching). Even though the mask doesn't
perfectly fit the character's changing sprite, keeping the mask a constant shape prevents characters from getting stuck in walls.
Also, I found the controls a little hard to use. The numpad for the three characters works well, but insert-home-pageup to switch was a bit confusing (my keyboard has them in a completely separate block than the numpad). Maybe you could just have it so jumping with a character also switches the view to them? Also, bare in mind that many laptops don't have a numpad. You may want to provide an "alternate" key for every key.
It's very easy to make alternate keys. Hell, just throw this code into some character's create event...
keyboard_set_map(vk_numpad7,ord("U"))
keyboard_set_map(vk_numpad8,ord("I"))
keyboard_set_map(vk_numpad8,ord("O"))
keyboard_set_map(vk_numpad4,ord("H"))
keyboard_set_map(vk_numpad5,ord("J"))
keyboard_set_map(vk_numpad6,ord("K"))
keyboard_set_map(vk_numpad1,ord("B"))
keyboard_set_map(vk_numpad2,ord("N"))
keyboard_set_map(vk_numpad3,ord("M"))
.. and it will make U, I, O, H, J, K, B, N, M function just like the numpad, in case the person's keyboard has no numpad.