In “Super Mario Land 2: 6 Golden Coins”, Mr. Miyamoto, the creator of Super Mario Bros., was interviewed about Super Mario Land 2 and told a story about Wario’s character development as follows
“During the development, we had a hard time making a character that looked-and-moved differently from Mario. So, I tried to make a slightly meaner character with the help of some staffs in the company. Then, I added an element in which Wario is able to do things Mario can’t by using his trunk (Which suggests that he has a large nose). And then, when it came out on the market, little children who played this game said ‘Hey! This guy is mean.’ or something like that, and it seemed as if they hated the character. That’s why I thought they didn’t like Wario. So, after a while, we tried to give him a more positive image.”

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In “Super Smash Bros. Brawl”, Wario’s character was designed with a fat and greedy look, which made his mean characteristics less obvious. In the expanded version of the game named “Super Smash Bros. for Wii U”, Wario was changed to be a bigger guy in order to make him seem more powerful.
In the GameCube version of “Super Mario Sunshine”, a little hint was given about the relations between Wario and Mario. In this game, Mario must search for 80 Shine Sprites by completing various tasks in each area. However, if he collects more than 80 Shine Sprites within a certain time limit, something else will happen. If he gets 8-8-88 Shine Sprites in 8 minutes, a secret cut scene is unlocked in the final part of the game. In this video, Mario gets excited that he will be able to get his own castle if he finds more Shine Sprites. Then Wario appears and tells him “Hey! I’m gonna build MY OWN CASTLE!”. Then Mario exclaims “Huh!? That’s MY line!”. It seems that Wario has the intention to steal Mario’s castle, which shows us the relations between these two characters.
How are they alike?
Mario and Wario are both plumbers that were born in the Mushroom Kingdom. Also, they both wear overalls, red hats with an M symbol on them, and moustaches. They are always together in many games except for “Super Mario Land 2: 6 Golden Coins” when Wario appeared as a rival character. From Super Smash Bros. Melee to Super Smash Bros. for Wii U, there are trophies in which they are both together in the same pose. Moreover, when Wario is selected in “Super Smash Bros”, Mario says “Better you than me!”. It seems that they know each other very well.
Mario and Wario are both good at doing business and they both have a similar personality to Donald Trump.
How are they different?
They each have unique characteristics and abilities, which makes them different from each other. For example, Wario is greedy and fat while Mario does not care about money and has always been considered to be thin in the games he appears in. Also, Wario’s favorite food is garlic and Mario’s favorite food is pizza. Wario has a shovel instead of hands and feet to dig holes while Mario uses his hands and feet to climb ladders and ropes to reach high places.
What would happen if they met?
It seems that Mario and Wario don’t like each other very much although they are both good at doing business. In a Comic strip called “Wario… Where?”, Wario looks at a mirror and thinks that he is the most handsome man in the Mushroom Kingdom, then Mario comes up to him and tells him that he has been looking for him because Peach’s castle is on fire. Then Wario replies as follows “Well! If it isn’t the goody-good plumber. What do you want?!
Conclusion
Wario and Mario are both plumbers but they have different characteristics, abilities, likes, and dislikes. If they met each other, they would fight due to their opposite personalities. It seems that Wario hates Mario because of his generosity while Mario does not really care about it. Also, he already has a girlfriend in the form of Peach. However, Mario and Wario always appear together in many games so they probably know each other well.