Retro Studios, Inc. is an American-based company and a subsidiary of Nintendo that developed the Metroid Prime franchise with the character Dark Samus, Mario Kart 7, Donkey Kong Country Returns and Donkey Kong Country: Tropical Freeze.
Frigate Orpheon, a location from Metroid Prime, appears as a playable stage in Brawl, with the Parasite Queen cameoing in the background. The tracks Vs. Parasite Queen, Vs. Meta Ridley, and Multiplayer (Metroid Prime 2) are directly ported from the Metroid Prime series, while the opening and menu theme are remixed into a new track for the game.
Several creations in Retro Studio's Metroid Prime series, including Samus Aran's Dark Suit, Dark Samus, and Meta Ridley, appear as trophies. Several other characters appear as stickers.
Dark Samus appears as an Assist Trophy in the game, using different Phazon attacks from the Metroid Prime series. Vs. Parasite Queen, Vs. Meta Ridley, and Multiplayer (Metroid Prime 2: Echoes) return from Brawl as music tracks, and Psycho Bits from Metroid Prime Hunters also appears as a track.
The Rainbow Road from Mario Kart 7 appears as a playable stage, with its theme ported directly from the game appearing on the stage as well. The theme also appears alongside the Rainbow Road themes from Mario Kart DS and Mario Kart: Super Circuit to form a Rainbow Road Medley. In addition, there is a music track called Circuit (Mario Kart 7), featuring the Circuit theme from Mario Kart 7 in Super Smash Bros. for Wii U.
Donkey Kong Country Returns is represented with a stage based on Jungle Hijinxs, the first stage of the game; it incorporates the layered design of the levels within Country Returns. The track Gear Getaway receives a new remix for the game, as well as the main theme of the game. The original version of the main theme, the Jungle Hijinxs level theme, and the Mole Patrol theme are directly ported from Donkey Kong Country Returns, and the Mangrove Cove and Swinger Flinger tracks are directly ported from Tropical Freeze.
Dark Samus appears as a playable fighter, as an Echo of Samus, and Meta Ridley appears as an alternate costume of Ridley. Frigate Orpheon reappears as a stage, and Vs. Parasite Queen received a new remix; all other Metroid Prime tracks appear in the Metroid universe's music selection. Previous Donkey Kong Country Returns, Tropical Freeze, and Mario Kart 7 music tracks return as well.