Game play is similar to that of The Subspace Emissary with few subtle differences, yet key differences. For starters, when fighting the last four bosses, you will have six stock lives rather than only having six stock lives during the final boss.
Character selection is the same save for one difference, you can swap out selected characters with non-selected characters in mid-level. For example, for on level your order could be Mario, Sonic, Captain Falcon, Ness. But you may be at a point in level where you might think that Donkey Kong might do better than Mario. Simply pause the game, go to an icon marked "Character Swap". Up comes a list of the characters you have chosen, select "Mario" and a list of the characters you didn't choose will appear. Select "Donkey Kong", then select "Swap" and Donkey Kong will take Mario's place. This can be done s many times as you like per level.
Again stickers increase a characters powers. Again stickers will not be allowed to overlap each other, but this time if you remove a sticker from your trophy, it is not lost but rather returns to your sticker book(what you keep the stickers in when they're not on the bottom of trophies). If a character has multiple forms(i.e. Zelda and Sheik) each form will have it's own individual trophy to put stickers on. A sticker that you put on the Zelda trophy may not be on the Sheik trophy unless you place the same sticker on each trophy. In the case of the Pokemon Trainers, rather than the trainers having their own trophies that effect all of their pokemon, each individual pokemon will have their own trophy to place stickers on.
Trophy Stands also reappear and have the same function. However, it will be easier to know when to throw them at an enemy or boss. The enemies and bosses will have blue health gauges that turn red to indicate that that particular enemy or boss has been weakened enough to catch with a Trophy Stand.