Super Mario Bros.: Sonic the Hedgehog is a ROM hack for the Nintendo Entertainment System that substitutes Mario with Sonic the Hedgehog while maintaining the original gameplay. In this version, Sonic runs continuously without player input. All text references have been altered to feature Sonic, and Toad now provides gameplay tips. The hack requires the Lunar IPS tool to apply to a Super Mario Bros. ROM.
As the name suggests, this ROM hack replaces Mario with Sonic, with the rest of the game left relatively untouched. Sonic always runs, regardless of whether or not you're holding the B button, all of the texts are changed from Mario to Sonic and Toad now gives you a useful tip.
This ROM hack is an .ips patch file, so you'll need Lunar IPS to apply this patch to your Super Mario Bros. ROM. The patch works for both Europe and Japan/USA regions.
Super Mario Bros.: Sonic the Hedgehog in Super Mario Bros. Game Wiki
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