In my D&D game, my party is knowingly using relic that will cast a supercharged Animal Shapes on the land- effectively changing the setting to a children's talking animal picturebook for 24 hours- any recommendations for an alternate system to use for this special weird session?
They know the relic to do something along the lines of "For 24 hours, changes all creatures in a 10 mile radius into various Beasts, who appear as shadowy, colorfully hand-drawn animals. Terrain changes to match- forests may be scaled up, cities may become burrow/prairie/treetop villages" Big ((GM DISCRETION)) disclaimer slapped onto the back of it of course. It changes the world into a storybook with storybook logic.
My/their intention is that this change would allow them to take a different angle at an upcoming danger, simplified greatly here-- a citywide system of many magical nodes all connected to a heavily-guarded underground vortex guarded by a small army; in 1 day, the nodes will trigger and each will funnel magical force from its area, effectively killing off or draining much of the city.
The storybook version would be different-- perhaps a redwall-esque story about a giant tree with a pit of eels and snakes below its roots.
My party is excited at the prospect of turning a gritty, protracted race to save the city into a more improvisational, cartoonish adventure. They only get one of these in the entire campaign and they want to use it here. I'm looking for the right system though. To use their regular stats eliminates the whole encounter concept, using their Beast stat sheets makes it a little boring. I'm looking at games like Lasers & Feelings, which could be changed into something fitting the setting easily, but I don't want it to be so lightweight that it's not interesting. I'm looking for a game that's a good balance of cartoony and easy to set up, while still having stakes and unique characters.
Any thoughts?