TMK | Super Mario Bros. 2 Madness | From Doki Doki Panic to SMB2
NES – Doki Doki Panic | Obscure Video Games
Panic! Nintendo NTSC-J (Japan) Video Games for sale | eBay
Found an NES version of Doki Doki Panic on eBay! Thought it'd be a hack of the original sprites on top of Mario 2 but this appears to be the original game!
Indie Retro News: Super Mario Bros 2 - The official romhack by Nintendo
Romhacking.net - Hacks - Super Doki Bros
Yume Kōjō: Doki Doki Panic/gallery | Nintendo | Fandom