Freaky green sunshine features a whole range of bosses that you will encounter through-out the game. The bosses work like in traditional games where you take a break from the normal action and puzzles to fight the boss. The boss battle is not only about shooting-to-kill but has more puzzle elements to it. Each boss has its own unique way of beating.
Here's an example of the "Killer Bus", one of the "mini"-bosses.
And here's an example of "Grim Donut" with his donut hat. Also showing a sample from a cutscene in the game. This is still work in progress and will look better when the game is finished.