Cute-'em-up

It's a parody of Gradius (geddit?) and as such, is a fully-fledged “cute 'em up.” The hectic sideways-scrolling action is every bit as intense as its namesake, but instead of battling spaceships and futuristic hardware you have sunny levels filled with cartoon penguins, giant clowns, flying pigs and all manner of bizarre things.

Source: wiktionary

Fantasy Zone was not a game meant to be taken as seriously as other shooters, and together with Konami's Twin Bee, it is credited by many for pioneering the cute shoot-'em-up, or “cute-'em-up sub-genre of shooters” (Kalata, “Spotlight”).

Source: wiktionary