The early Japanese mobile scene had a surprising amount of freeware and homebrew games. Check out ApeMan, a Super Mario inspired platformer featuring a giant ape. The best part is the button that lets you pick your nose!
https://youtube.com/shorts/B3fmk--XZGA
https://youtube.com/shorts/B3fmk--XZGA
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IIRC Cheetahmen was a very early meme that took off in Japan...
There were also actual Mario ROM hacks, since that was big too.
https://www.youtube.com/watch?v=7VEfVGLMPjc