This page explains in detail the interactions between the Astal series and the Mario series.
Astal[]
Mario's sprite ripped from Astal.
April 27, 1995
Astal
Mario
A sprite of a character that looks almost exactly like Mario can be found in the code of Astal through hacking, but it's unused in the actual game. It's unknown if the character was scrapped from the game during development, or if it was used as early test graphics. It's also possible it was created as an Easter egg.
Note that he's depicted with blue shirt and red overalls, like in Mario's first appearances, and has no gloves.
License[]
Astal's company Sega had no right over Nintendo's character Mario, and this may be the reason for the sprite not being included in the actual game.