Prism Tower (stage)

Prism Tower (Japanese: プリズムタワー Prism Tower) appears as a playable stage in Super Smash Bros. for Nintendo 3DS and Super Smash Bros. Ultimate. The stage was first revealed on Nintendo's Miiverse service on March 11, 2014. Battles take place within Lumiose City, primarily at and around the Prism Tower as it appears in Pokémon X and Y. Matches begin on the ground level in front of the tower, and players must climb the tower by securing footholds (such as moving platforms). As the stage ascends, the background scenery changes to a different time of day. Like many other Pokémon series stages, various Pokémon can appear in the background, though none have an effect on gameplay.

SmashWiki

SmashWiki has more about this subject:

Prism Tower

Bulbanews

Bulbanews has an article related to this subject:

Lumiose City to be featured in Super Smash Bros.

Pokémon

Pokémon		Appearance
	Helioptile	Appears on the ground.
	Magnemite, Zapdos, Emolga, and Yveltal	Appear from the platforms.

Trophy information

Prism Tower also appears as a trophy exclusive to the 3DS game.

NA: A notable location from Pokémon X and Pokémon Y. The Prism Tower is the symbol of Lumiose City, the metropolis at the heart of the Kalos region. In this game, platforms will take you on a tour around the tower and its surrounding areas, and at night you can marvel at the fabulous illuminations. You may see different Pokémon, as well.

PAL: A notable location from Pokémon X and Pokémon Y. The Prism Tower is the symbol of Lumiose City, the metropolis at the heart of the Kalos region. In this game, platforms will take you on a tour around the tower and its surrounding areas, and at night you can marvel at the fabulous illuminations. Of course, you may run into a Pokémon, too.