Sinistar, but instead of bombs you're throwing cute forest critters at the unstoppable horror. Really gives the whole game a darkly comedic feel, which makes it fun and memorable.
My only real gripe is that the individual character abilities, while an interesting idea, never really seemed to matter. No matter who I had in my roster, my strategy amounted to "throw them as fast as possible at the nearest critter, convert, repeat." This is understandable given its nature as a game jam game, though, and I think there's a lot of potential if you ever decide to expand on it.