>Speculation
Sure. Here's my shit.
>Princess Peach is a toad, but a royal strain that looks humanoid when they grow up. Normal toads remain the same, but some female toads (Toadette) can mature with the use of the Super Crown, which is a pheromone connected to a device that allows the female toad to absorb nutrients
>Coins in the Mario world are renewable and naturally occurring, but they still have to be minted. Some coins have a star emblem (SM64), others just the regular I. Think Superstar Saga's explanation with blocks. Some coins can be smelted and their form or colors change (Red coins, blue coins, etc.)
>Bowser, Jr. and the Koopalings come from a royal strain of Koopa that breathes fire. Breathing fire as a Koopa is considered a rare trait. Some exceptions may be the Fire Bros., which are rarely encountered
>Dry Bowser is Bowser's Brother from SMB2JP
>The Golden Statue of Peach from Wario Land 1 became Pink Gold Peach. How? Magic
>The mandate was real, but it was a guideline more than anything else. Basically a list of do's-and-don't's. Sometimes it fluctuates depending on the situation. It's likely still in place. Every company has a 'mandate'