A few games on the NES seem to have some interesting relationships to Nintendo’s flagship Super Mario Bros. game. For example, here’s Kid Kool, whose main character happens to share the exact same walk cycle as our hero Super Mario:
Even the pint-size version has a few distant cousins, shown here with Bomber Man and Challenger:
There are likely other games, too. The theory we had was that Mario was passed around as an example in a devkit, and some early games simply modified and reused some of the graphics. For the most part, though, nobody ever really noticed.