Super Mario Bros. 2

American Super Mario Bros. 2 is the 'strangest' Mario game: it was actually Doki Doki Panic, a Japanese game with different protagonists, reskinned with Mario because the real Japanese SMB2 was deemed too hard for the West. The result was paradoxically innovative: 4 characters with different abilities (Peach could float!), vegetable picking, unique bosses like Birdo. Many elements — Shy Guys, Bob-ombs, Birdo — became canon in the franchise.