Sticky Situation
Uncommon37.9%ObjectiveOptionalAnywhere
Survive the slime rain, where gelatinous organisms fall from the sky in droves.
Slime Rain is a random daytime event - slimes fall from the sky until you've squashed enough of them (around 150), at which point King Slime himself drops in. Survive to the end (i.e. see the King off, Slippery Shinobi) and it pops. It happens on its own; just don't hide indoors when it starts.