Retro Studios, Inc. is an American-based video game development company and a subsidiary of Nintendo. Founded on September 21st, 1998 and officially launching on October 1st of that year, Retro Studios was conceived as an alliance between Nintendo and Jeff Spangenberg to develop more mature titles for the upcoming GameCube. Initially headquarted in Spangenberg's house, the quickly growing team moved to an office in early 1999 and immediately entered four different titles into preproduction. These titles include an American football game titled NFL Retro Football, a role playing game titled Raven Blade, a vehicular combat game with the working titles Car Combat and Thunder Rally, and an action adventure game with the working title Action-Adventure. None of these games were making significant progress before Shigeru Miyamoto visited the studio in 2000. He was overall disappointed in what he saw, but thought there was potential in the engine they made for Action-Adventure, which he suggested would work with a new Metroid game. After receiving the license to make a Metroid game, all four previous games were canceled and their staff were moved to work on what would become Metroid Prime. On May 2nd, 2002, Nintendo purchased Retro from Spangenberg, and reclassified the studio as a first party developer. Spangenberg would later found Topheavy Studios, whose first and only game, as well as the last game which Spangenberg was credited on, was The Guy Game.
After the critical and financial success of Metroid Prime, Retro would work on two sequels, Metroid Prime 2: Echoes and Metroid Prime 3: Corruption, as well as remaster the trilogy and collecting them into the Metroid Prime: Trilogy. Retro would then develop for the Donkey Kong franchise with Donkey Kong Country Returns and Donkey Kong Country: Tropical Freeze. Retro would also collaborate with Nintendo EAD on the development of Mario Kart 7. On January 24th, 2019, Nintendo announced that they were not satisfied with the development of Metroid Prime 4 under its original, unannounced developer (allegedly Bandai Namco), and the project would completely restart under Retro. Metroid Prime 4 is currently in development with no official release date.
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. Multiple Retro Studios-created Donkey Kong and Metroid characters also appear as Spirits.