Mario & Sonic

The Mario & Sonic series is a collection of crossover sports games produced by Sega. It features characters from both Nintendo's Mario franchise and the Sonic the Hedgehog franchise. It is the first time where former mascot rivals Mario and Sonic appeared together in a video game. Since Super Smash Bros. Brawl, they also appear together in the Super Smash Bros. series.

The series began when Sega acquired the license to create video games based on the Olympic Games, intending to create a version featuring Sonic the Hedgehog characters. Due to the atmosphere of competitive sportsmanship the Olympics had to offer, Sega received approval by Nintendo to include Mario characters in the game, somewhat reflecting their past real-world history as mascot rivals. The Mario & Sonic series has been overall well-received by the media, mainly for being a crossover between Mario and Sonic, with the gameplay and multiplayer having been praised as well. However, Mario & Sonic has been criticized for the choice of setting for both series, the controls, and having the Olympics be the only theme in the series.

Playable characters
Not including supporting characters, the series has spawned a total of 43 playable characters - 22 from the Mario series, 20 from the Sonic the Hedgehog series, and Mii characters. Listed in the table below are which characters appear in each individual installment.

All-Around
Characters in this classification have a equal balance of speed, acceleration, power, skill and stamina.

Speed
Characters in this classification have high speed and acceleration, but poor skill, power and stamina.

Power
Characters in this classification have high power and stamina, but have poor speed, acceleration, and skill.

Skill
Characters in this classification have high skill, and have an average balance of speed, acceleration, and stamina, but are weak in power. In Mario & Sonic at the Olympic Games Tokyo 2020, this category was renamed as "Technique".

Mobile phone tie-ins
The Mario & Sonic series consists of a few mobile game tie-ins, although none of them consist of elements from the Mario franchise.

Following the release of Mario & Sonic at the Olympic Games, Sega published Sonic at the Olympic Games, a Java-based mobile phone game that features characters from the Sonic the Hedgehog franchise competing in the 2008 Beijing Olympics. Despite the similar premise, no Mario characters or references appear in the game.

Sega would publish another mobile title shortly after the release of Mario & Sonic at the Olympic Winter Games, called Sonic at the Olympic Winter Games, this time on iOS. It also features characters competing in the 2010 Winter Olympics. It was taken down from the App Store shortly after release, without any specification.

Another game called Sonic at the Olympic Games, set during the 2020 Tokyo Olympics, was released worldwide for iOS and Android on May 7, 2020.

Trivia

 * As the announcement of the Mario & Sonic Olympics video game series was revealed (starting with Mario & Sonic at the Olympic Games), the agreement was also reached that in the case of publishing and marketing duties for each Mario & Sonic Olympics installment, Sega would handle the process for all territories outside of Japan while Nintendo would handle the process inside of Japan itself. The fourth game, however, was published by Nintendo outside of Japan rather than Sega. Nintendo has since published subsequent titles globally as well.
 * Since the start of the series, neither the in Pyeongchang, South Korea nor the  in Beijing, China have had Mario & Sonic games to coincide with their events. In the former's case, Ubisoft acquired the rights to make video games for the PyeongChang 2018 Olympic Winter Games before Sega could.
 * Bowser and Peach are the only playable Mario characters to change their voice actor during the series (the former switching from Scott Burns to Kenny James in the third installment and the latter switching from Jen Taylor to Samantha Kelly in the second installment). Conversely, Dr. Eggman and Eggman Nega are the only playable Sonic characters to keep their English voice actor in every installment (keeping Mike Pollock as their voice actor).