ideas
Basic goo creatures would involve an Oozle mixing with one of the various "leaky creatures" i.e. stickies, melties, inkies, what happens is that the oozle now has three small circles inside of it. Each hit "since it takes three" will release one of the circles of inner working goo. Like is they mutated with a stickie every hit sends a splash just like one if you were to kill a regular stickie, but this time the oozle just keeps going after you, still killing you in one hit.
My next idea would be many more reverse mitosis's, again working with the leaking goo's, what happens is they still die in one shot but they randomely "or every few seconds or so" automatically splash the inner goo.
Next is sharp and clutter. What happens is they form a sort of turret that shoots spikes at you. Not like a horror where it is a circle, but more concentrated spikes into the player's