The game takes place during the Beijing 2008 Olympics in China, though set in a Mario/Sonic universe that features Mario and Sonic characters and themes. Players will be involved in multiple different Olympic-styled games, and will be able to play as one of 16 different characters, eight from each series.
Although both Nintendo and Sega worked on this collaboration, most of the development was handled by Sega. However, as the game was completed, Sega did publishing and marketing duties for all versions outside of Japan, South Korea, and Taiwan. Nintendo did publishing and marketing duties for the Japanese, Korean, and Taiwanese versions of this game.
The game is noted to be the first game in which the two famous characters meet each other. However, while essentially this is true, it should be noted that in Donkey Kong Country 2, you were able to see Sonic's shoes next to a trash can, a bash at SEGA from Rare Ltd.
Another first in the game industry is Miis meeting Mario. In the game, you'll also be able to play as the customizable characters that you create in the Wii hard drive, and thus compete with them against the most famous video game icons.
Players are separated not only by team (Team Mario and Team Sonic), though also by their specific advantages. These advantages include power, skill, speed, and stamina, and two characters from each team will be involved in one of these. For example, Yoshi and Daisy from Team Mario are masters at speed, while on the Sonic side Sonic the Hedgehog and Shadow are. Both versions of the game use the new functions of these consoles completely. The game was compatible with Nintendo Wi-Fi Connection.
Originally, Mario & Sonic at the Olympic Games was considered an April Fools joke, as the game was revealed on March 28, 2007. However, soon after, Sega stated on their official website that the game is official, and that both Sega and Nintendo are working on this game project. Shigeru Miyamoto then soon confirmed that he would be supervising the project, confirming Mario & Sonic at the Olympic Games to be real.
The game includes 20 different Olympic sports, dramatically rivaling that of the 5 in Wii Sports. Each one requires you to use the Wii remote or nunchuk in one way or another. The following will take a look at every game that is included.
- Mario - All Around
- Luigi - All Around
- Princess Peach - Skill
- Yoshi - Speed
- Princess Daisy - Speed
- Wario - Strength
- Bowser - Strength
- Waluigi - Skill
- Sonic the Hedgehog - Speed
- Miles "Tails" Prower - Skill
- Amy Rose - All Around
- Shadow the Hedgehog - Speed
- Dr. Eggman - Skill
- Blaze the Cat - All Around
- Knuckles the Echidna - Strength
- Vector the Crocodile - Strength
The DS has 24 different events (most of which must be unlocked), including 8 'dream' events, many of which use the stylus.
- 100m: Stylus
- 400m: Stylus
- 400m Hurdles: Stylus
- Long Jump : Stylus
- Triple Jump: Stylus
- Javelin Throw: Stylus
- Hammer Throw: Stylus
- Race: Stylus
- Canoe: Stylus, Arrow Keypad, LR buttons
- Boxing: Arrow keypad, AXY buttons, LR buttons
- Long Jump: Stylus
- Table Tennis: Arrow keypad, ABXY keypad
- Fencing: Stylus
- Shooting: Stylus
- Basketball: Stylus
- Archery: Stylus
- Table Tennis: Arrow keypad, ABY buttons
- Fencing: Stylus
- Shooting: Stylus
- Cycling: LR buttons
On February 12, 2009, it was announced that to honor the upcoming 2010 Winter Olympics in Vancouver, Canada, SEGA and Nintendo would release Mario & Sonic at the Olympic Winter Games for the Wii and Nintendo DS in late 2009. This eventually started an annual series, with a new game every Olympic Games and/or Olympic Winter Games. Following games include Mario & Sonic at the London 2012 Olympic Games for the Wii and Mario & Sonic at the Sochi 2014 Olympic Winter Games, with a 5th game in development.
- The game was originally planned to include more characters like Donkey Kong and Silver, whom were both scrapped but later introduced in the sequels. A clip has emerged of missing characters in the game's files accessible by hacking, which include Cream the Rabbit, Jet the Hawk and bizarrely, a Goomba. 
- This is not the first time that Mario takes part in the Olympics. He also competed in an event called "Intergalactical Olympics" in the Club Nintendo comic "Super Mario: Verloren in der Zeit".
- The DVD set of The Adventures of Super Mario Bros. 3 was re-released in a double pack with The Adventures of Sonic the Hedgehog Volume 1 to tie in with the release of this game.
- A version of this game was also released on mobile phones in June 2008, but lacked Mario characters and only included Sonic characters. Because of this it was simply titled Sonic at the Olympic Games.
- Princess Peach and Princess Daisy were originally going to have swimsuits for the aquatic events. However, this idea was rejected by Nintendo. Eventually, Peach, Daisy, Amy, and Blaze were given swimsuits in Mario & Sonic at the London 2012 Olympic Games.
- Nintendo's official US site for Mario & Sonic at the Olympic Games (Wii version)
- Nintendo's official UK site for Mario & Sonic at the Olympic Games (Wii version)
- Nintendo's official Japanese website for Mario & Sonic at the Olympic Games (Wii version)
- Wii Wiki page