World 8 (New Super Mario Bros. Wii)
From the Super Mario Wiki
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The Fortress here leads to a fight with Magikoopa, who previously in the game is only seen enhancing the Koopalings when the heroes reach them in castles. This world also features the third and final fight with Bowser Jr., once again on an airship. The final level features the two-part final battle with Bowser, who is not once seen in the game up until that point. The Enemy Course in this world is Podoboos between 8-3 and World 8-Tower on the bridge.