There's something special about Waluigi. Something that makes fans have particularly strong feelings either for or against him, something that saw him win an official Valentine's Day poll, and something that makes people want to see him run around a Mario Kart circuit without being in a car apparently.
Mod developer Niment has transformed the character in Mario Kart Wii, stripping away his vehicle and having him charge around the track like the absolute champion we all know him to be. To do it, Niment actually used Waluigi's model and animations from Mario Party 9, and you'll notice that he even reacts to certain situations like going over speed boosts and running into obstacles. It's a pretty solid effort.
The very same person has also released similar versions of the mod for Luigi and Wario (you'll spot Wario at the start of the video), seemingly being intent on creating some kind of 'Mario Kart: But Not Actually In Karts Deluxe'. To be fair, we could happily sit and watch Waluigi sprinting by his bemused opponents all day long.
Sometimes you just don't know you want something until you see it.