Waluigi's Extreme Height Might Make Him A Nintendo Titan
While it's hardly a matter of concern for most people, it's no secret that Nintendo tends to be inconsistent with the size of characters in the Super Mario franchise. It is, after all, a cartoon universe, where features are deliberately exaggerated for effect; Mario and Luigi wouldn't be nearly as endearing if they had realistic head and leg proportions. Perhaps one of the hardest Super Mario characters to pin down is Luigi's evil doppelganger, Waluigi. Fan calculations have put Waluigi's height anywhere from below average to extremely tall, but his true measurements may depend on the sources used and how the math is done.
The character isn't in every Mario game, being a relatively late addition to the canon. Waluigi's first appearance was in 2000's Mario Tennis, serving (literally) not just as a foil for Luigi but as Wario's doubles partner. He's been largely absent from the flagship series, instead appearing mostly in sports-themed spinoffs and Mario Kart - even Super Smash Bros. has excluded him. This makes it a little tougher to determine Waluigi's measurements, but it's not impossible.
One of the more probable answers comes from The Game Theorists on YouTube, which cites models extracted from games like Mario Kart Wii and imported into the 3D modeling tool Blender. That data put Waluigi at 7-foot-7, absolutely dwarfing Luigi and Wario's 5-foot-9 frames - presumably because of his gangly legs. This calculation is backed up, to a weaker extent, by another fan's pixel count on the Character Stats and Profiles Wiki. Using unspecified character screens, the fan measured Mario at 256 pixels tall versus Waluigi's 335. Working off a figure that put Mario at 5-foot-9, Waluigi once again hit 7-foot-7. There have been taller people in the real world (the tallest known person being Robert Wadlow, who reached 8-foot-11), but these measurements still suggest Waluigi would tower over most other Nintendo characters.
One chart, however, created by DeviantArt user sesshowmall, claims Waluigi is just 4-foot-7 (or 5-foot-2, when standing fully upright). That's relative to a 3-foot-3 Mario, a 3-foot-7 Wario, and a 3-foot-9 Luigi. The methodology used is debatable, being based on Mario's size versus objects like taxis and fire hydrants in Super Mario Odyssey, as well as Sonic's official 3-foot-3 height in Mario & Sonic at the Olympic Games Tokyo 2020, where Mario is comparable. To be accurate, of course, would require measuring Waluigi directly.
Confusing things further, the Super Mario Odyssey version of Mario could also be 5-foot-1, according to The Game Theorists' measurements relative to in-game distances counted in meters. That would, however, make New Donk City's people, cars, and buildings enormous, when they appear to be the most realistically proportioned items in any Super Mario game. In truth, the most that can be said with objectivity is that Waluigi is one of the tallest characters in the series' universe.
Source: The Game Theorists