Sega (also referred to as SEGA) is a Japanese video game company. Its mascot is Sonic the Hedgehog, having replaced Alex Kidd in 1991. In the past, Sega used to be the rival company of Nintendo. As such, both engaged in frequent bouts of competition.
An early mockery toward Nintendo happened in Alex Kidd's final game, Alex Kidd in Shinobi World, where the first boss was originally going to be named Mari-Oh, a parody of Mario. However, it was changed to Kabuto. There are also characters called the "Marxio Brothers" in a British comic called Sonic the Comic.
To counter these mockeries of Mario, Rare had Sonic and another Sega character, Earthworm Jim, make "cameo appearances" in Donkey Kong Country 2: Diddy's Kong Quest. Their equipment, Sonic's shoes and Earthworm Jim's blaster, are seen next to a trash can during Cranky Kong's contest labeled "No Hopers".
Move to software developer
This feud lasted for many years, until Sega became a third-party developer in 2002 with the closing of their console-producing division with the discontinuation of the Sega Dreamcast in 2001 in North America, in Europe in 2002, and in Japan, where the Dreamcast continued to be produced until 2007. Sonic Adventure 2: Battle, a port of Sonic Adventure 2 for the Dreamcast, marked the first appearance of a Sega game on a Nintendo console, specifically the Nintendo GameCube. With that, the feud ended, and the two companies began collaborating. Their first effort resulted in F-Zero AX/GX. The two companies later teamed up to create a crossover game featuring both Mario and Sonic, Mario & Sonic at the Olympic Games, which generated four sequels: Mario & Sonic at the Olympic Winter Games, Mario & Sonic at the London 2012 Olympic Games, Mario & Sonic at the Sochi 2014 Olympic Winter Games, and Mario & Sonic at the Rio 2016 Olympic Games. Sonic also appeared as a playable character in Super Smash Bros. Brawl, being one of two characters (the other being Solid Snake from the Metal Gear franchise) in the game that did not come from a Nintendo-owned franchise. He reappears as a playable character in Super Smash Bros. for Nintendo 3DS / Wii U. Additionally, Mario himself was going to appear in Sonic & Sega All-Stars Racing as a character exclusive to the Wii version, but was taken out after Nintendo and Sega agreed that Mario/Sonic crossovers were best suited for the Olympic Games series, despite the fact that Sonic had appeared previously in Super Smash Bros. Brawl, and that there was already a racing game featuring Mario out for the Wii.  Aside from Olympic Games and Super Smash Bros., Sonic has made cameo appearances in the Mario universe. By using a Sonic amiibo, players can unlock an outfit based on Sonic in Yoshi's Woolly World, Mario Kart 8, and Super Mario Maker. Yoshi's Island Zone is a downloadable level in the Wii U version of Sonic Lost World which features Sonic in Yoshi's Island.
Sega currently makes games for Wii U, Nintendo 3DS, Xbox One, PlayStation 4, and iOS and Android devices.
Mario games developed by Sega
Mario games published by Sega