Some bugs/glitches/oversights I've found:
If you touch the lava after switching, the level doesn't end. On reentering the character, if they are still in lava, the level ends.
If you jump into and hold against the other character, you can surf them
You can switch character and fire arrows during the level end and game over screens. The wall also continues to move, until it reaches your character
If you jump against a wall or door, you can keep some height, and surf along it for a bit.
You can stand in windows, which would let you skip activating the button in the first lava room, if you could jump off the platform with the bow (wall surfing doesn't give enough height).
You can press buttons repeatedly, which causes an earthquake
Players can stand on opposite colored buttons and still clear the level
You can right click the buttons on the game over screen. I have accidentally exited to main menu too many times because of this
Edit for additional:
If a character picks up a bow while in the transition animation, it appears in the other character's hands
Characters can hit buttons while not active
You don't have to look at buttons to press them