Wario

Wario is Mario's evil alter-ego, when Mario quit, they tried to replace him, so Wario was the 1st choice.

Birth and childhood
Wario was born in Brooklyn, for the longest time, he often bullied Mario,until Mario kicked his ass, Wario was angry so he trained to become strong, despite being fat, he has a ton of arm muscle.

Personality
Wario is very greedy, he often robs banks and shakes random enemies for money, he only goes on adventure for money, and nothing else, he thinks everybody else can go fuck themselves, he only cares for the $$$$

Nintendo hiring
After Mario quit, Nintendo hired Wario, Nintendo had some inital problems, but Wario games became a huge hit, and he has appeared in games like Super Wario Bros,Super Wario Galaxy and Wario's Money Grab, Wario then got so rich that he quit and went on a quest to become the world's richest man.

Now
Wario commonly shows up for the Mario Kart Tournament and other major events, otherwise he is just finding treasure.