The previous game, Super Smash Bros. Melee, featured Pokemon Stadium, but it’s been upgraded for this game into Pokemon Stadium 2. This time around, you’ll see guest Pokemon appearing in the background.


Ordinarily, it’s a fairly orthodox stage when nothing special is happening. But as time passes, the terrain transforms into four different types: "Electric," "Ground," "Flying," and "Ice."


When it transforms into Ice, things get extremely slippery!


A mountain of earth appears in the middle of the screen for the Ground stage!


On the Flying stage, everyone’s jump abilities get boosted!

For these four transformations, we’ve chosen types that were not present in Melee. Terrain that changes suddenly makes fights excitingly unpredictable.

Source: http://www.smashbros.com/en_us/index.html