Your headcanons

Tatanga was Wario's best friend once, but then he kept sponging off Wario so he was dumped and Wario invented a new best friend by splicing some DNA he got from Luigi with an eggplant.
 
Toad is a closet gay with a crush on Mario.

Blue Toad and Yellow Toad are brothers and the co-commissioners of Mario Party.

Toadette is Toad's sister.

Toadsworth is the widower of Grandma Toadstool and Peach's grandfather.
 
Magikrazy said:
If she wore her mushroom cap, she couldn't wear her crown.
Or recessive genes... Grandma Toadstool may or may not be human. We don't know, nor have we seen her or heard of her before now.
 
Mario donates a lot of the coins he gets in his adventures to the less fortunate. Thats why he is generally seen as living very modestly.