Drawing on New Super Bros U as its main source of inspiration, Mushroom Kingdom U is another stage in Smash Bros that transforms constantly throughout match. While the terrain changes are not too threatening in and of themselves, players do have one major annoyance to watch out for in the pesky Nabbit. In modern Mario games Nabbit is pretty much a fleet-footed thief, and players are challenged with catching up on him for a reward by chasing him through a stage and its perils at top speed.
In Smash Bros though, Nabbit has nothing for you. Instead, you're the one he's trying to steal! Nabbit will walk and leap through the stage periodically and make a leap toward an unfortunate fighter, stuffing him or her into his expansive bag if he hits his target. Once this is done Nabbit will begin to take off to the top of the stage, resulting in an instant KO. The good news is that it's not the end if you get caught, players can potentially break free with enough struggling. If Nabbit grabs you, smash buttons and spam your directional controls.
Although there are always exceptions, most of the time it's a waste of time to battle Nabbit. He will flinch from attacks, but there is no getting rid of him and he will aggressively chase you the way the more stubborn assist trophy characters do. In the end, the best defense against Nabbit is to keep your distance during a match.
The good news is that Mushroom Kingdom U offers plenty of warning as it changes. Every now and again the koopa Wizard Kamek appears to transform the stage with magic in a process that takes several seconds, and the cue is transparent between his cackling chuckle and flight across the stage. Even the most combat absorbed player should not be caught off guard by changes on this stage.
As for the stage itself, let's tour Mushroom Kingdom U!
Mushroom Kingdom U begins simply enough with three elevated platforms upon a large amount of solid ground. At times additional platforms will appear in the form of block platforms that expand and shrink sideways the way they do in Super Mario World, or a number of branches from a tree that spontaneously grows in the background. These will likely appear only if the stage cycles back around to this point, though.
Screen 2: Cloudy Sunset
Here we have four platforms and less room to manuver, complete with bottomless pits waiting to swallow the careless. Complicating matters is the fact that this is a common place for Nabbit to show up, while periodically large icicles can descend from the sky here and elsewhere in the stage. Ordinarily these simply creative temporary platforms on which to fight, but they can mean trouble if they fall directly on top of a fighter. In this area, staying still is not a good idea. Heavier and slower fighters have the most to worry about.
Screen 3: Rotating Platforms
This area takes you in doors where two long platforms will perpetually rotate, constantly expanding and contracting the stage. This can turn disadvantageous all too quickly in a pitched fight, and fighters would be smart to stay nimble and prioritize staying on the top. Waiting until the last moment to reach safe ground is a good way to set yourself up for a KO against a tougher opponent.
Screen 4: The Toppling Platform
The base of this stage is like an unstable Final Destintion. Instead of staying flat the platform will tilt left and right, resulting in a stage angled more often than not that can prove annoying for those that prefer ranged attacks. Adding to the tactical challenge here is the presence of two layers of moving platforms that move across the stage up above, which advance at a hasty pace. These can be useful for those confident in their air game, just don't linger lest you find yourself taken to the edge of the stage.