Since the evil twin concept is common in video games, perhaps it was only a matter of time before one was introduced for Mario. The thing is, Wario isn’t actually Mario’s twin or doppelganger, and the two of them are supposed to have known each other from the past. So is it just a coincidence that Wario looks like a fun house mirror version of our favorite plumber? Well, there’s apparently been some speculation that they might be cousins, but I don’t think it’s ever been officially explained. After Wario is introduced, he’s just kind of there. He’s first introduced in Super Mario Land 2, in which it’s explained that the plot of the first Super Mario Land game was part of his plot. Wario hired the space alien Tatanga to kidnap Princess Daisy so that he would have a chance to conquer Mario’s own country. Mind you, this is the first we heard that Mario HAD his own country, and he presumably doesn’t spend a lot of time there since he’s usually in the Mushroom Kingdom (maybe Mario Land is his vacation home or something), so why Wario had to create a distraction to get him to leave this time isn’t really clear. Nonetheless, Wario is the main villain in this and some other games, but it isn’t long before he starts being used as a protagonist. He’s essentially an antihero, motivated almost entirely by greed. In his more recent appearances, though, he isn’t so much a thoroughly bad guy as someone who’ll take whatever side benefits him the most. In the DS version of Super Mario 64, he’s playable along with Mario, Luigi, and Yoshi.
Luigi eventually received his own similar-looking rival in the form of Waluigi. When I first learned about this character, I thought they really didn’t put a lot of thought into his name. Since the upside-down L on his hat looks more like a Greek gamma than anything else, why isn’t he “Guigi” or something? From what I’ve heard, both Wario and Waluigi’s names are derived from the Japanese “warui,” meaning “evil.” This might mean that the symbol on Wario’s hat being an English W wasn’t even intentional, although I would think the designers would have to have been aware of the connection. Anyway, while Wario is cartoonishly obese, Waluigi is incredibly tall and skinny. It’s apparently never been confirmed that Wario and Waluigi are brothers (some sources suggest they are and others that they aren’t), so that adds an extra degree of complication into their relation to the Mario Brothers. Waluigi is angry, arrogant, and self-pitying; and his bits of dialogue in Mario Kart Double Dash suggest that English might not be his first language. (“Waluigi no win this time!”) His first appearance is in Mario Tennis, and since then he’s become a fixture in the sports spin-offs and Mario Party games. He hasn’t appeared in any of the regular platform games, even the ones starring Wario, though, and I have to wonder if he ever will.
One interesting bit about Wario and Waluigi that I’ve seen noted on the Internet is that, in a flashback episode of the Super Show that tells how the Mario Brothers first became plumbers, two of their fellow plumbing academy attendees kind of resemble the nasty pair.
This was before the characters were introduced, so I’m sure they were really just extras drawn to look kind of like our heroes (never underestimate the laziness of the animators on shows like that), yet I don’t know of any reason why all four characters having attended the academy together couldn’t mesh with the back story as we know it. In the show, Mario and Luigi are said to be from Brooklyn, and Wario’s accent in the games certainly suggests that he might well be from New York City as well.
Do any other main characters in the series have evil doubles? Well, in Super Mario RPG, we’re introduced to Yoshi’s rival, a bossy Blue Yoshi with sunglasses. His name is Boshi in the English translation, but in Japanese it’s Washi. Since Nintendo doesn’t hold all of the rights to the original characters in this game, I tend to doubt we’ll see Boshi team up with Wario, but it would be interesting.