This page explain the link between the Mario series and the game Alex Kidd in Shinobi World, part of both the Alex Kidd and the Shinobi series.
Shinobi Kid[]
Boss battle with Mari-Oh and the description screen for Round 1.
Alex Kidd
Mario
Mario
Shinobi
During the development of Alex Kidd in Shinobi World, while it was going to be called Shinobi Kid, the first boss of the game was "Mari-Oh", a parody of Mario and Shinobi's first boss, Ken-Oh. By the final game, Mari-Oh was replaced with the unrelated "Kabuto" boss.
Because Shinobi Kid wasn't originally intended as an Alex Kidd game, this unreleased link may be considered only between the Mario and the Shinobi series.
License[]
Alex Kidd in Shinobi World's company Sega had no right over Nintendo's character Mario, in fact they only wanted to include a parody of the character, not actually him, but finally they decided to remove him from the game.