Doki! Doki! Panic is the game that Super Mario Brothers 2 was based on. When Nintendo released Super Mario Brothers 2 (The Lost Levels to us Americans) in japan, its popularity was eclipsed by this game, which came out at about the same time. So Nintendo in all their wisdom decided to hack some Mario characters into it and release it as SMB2 stateside. There’s a few more differences than the character changes, though they don’t really amount to much. Gameplay wise, this is almost exactly the same as SMB2, so if you’re a fan of that game, or of the Mario series in general, you should give this one a whirl.