Here's a tentative submission, I'll see if this pans out and consider removing it.
Waterfall is an area in Undertale, a 2015 RPG that was an almost instant hit. Waterfall is a midgame location, with beautiful scenery that contrasts very well with the armed soldier trying to kill you. The Smash incarnation of the stage is something of an amalgam of different parts of Undertale’s Waterfall. The main platform uses the standard type of rocks found in Waterfall, and the floating platforms resemble the bridges seen in the Undyne chase scenes. Waterfall has waterfalls that flow on both sides of the stage, but like the ones on Kongo Falls they’re a background element and can’t be swam in. New Home can be seen in the distance. The stage is NOT pixel art, everything is updated to high quality 3D models.
The stage’s central gimmick are the Bridge Seeds. Bridge Seeds occasionally spawn like items do, out of the sky at random. They spawn about as often as items when set to “rare”. The way they spawn doesn’t consider them an item, meaning they spawn at the same regardless if no items or every item is activated. They can be picked up like items (they make the little squeak sound from Undetale upon being picked up). Unlike in Undertale, they are held in the hand instead of on the head. They act like standard items (such as the Pokeball and Smoke Ball), being able to be thrown around and replacing most imputs.
Bridge Seeds can’t hurt enemies, and if they touch the ground nothing happens. Pretty useless, right? No quite. If thrown down one of the sides of the stage, it blossoms and expands backwards, making a new platform! Bridge Seed Platforms are roughly one Training Mode Block tall and wide. They don’t have ledges, so they are mostly helpful for opponents launched upwards, not downwards. The small size makes it a poor camping place, as they can’t roll away or anything. After 45 seconds, the Bridge Seed Platform gets lost in the current and falls down. The Bridge seeds don’t spawn on the hazardless version of the stage. Rarely, upon selecting the stage, various parts of waterfall’s scenery spawn in the stage’s background (Echo Flowers, Sans’s sentry stand, and a vacant Dummy, among others). Pressing ZL and ZR puts this stage in “battle mode”. Everything but the fighters are in black and white. The textures of the parts of the stage are altered to make this look not terrible.
i'm playing with fire, let's see if the gamble pays off