First reported by DSOGaming, modders Zoft and Triggerhappy have introduced crouch walking to Metal Gear Solid 3's Master Collection port on PC. The intermediate movement option between upright locomotion and belly crawling was embraced by later Metal Gear games, but Snake Eater's 3DS port was previously the only version of the game to feature the movement.
Back in '04, Naked Snake could walk upright, or he could crawl around on his belly—no middle ground, and this was the case in prior MGS games as well. I don't know how often you find yourself crouch walking to be sneaky in real life, but it seems to have become our videogame shorthand for "stealth mode," and it can be kind of jarring to go back to one of the granddaddies of the stealth genre and not have the option.
Zoft and Triggerhappy ported the 3DS port's crouch walk animations into the Master Collection version of the game, and have been working on fully integrating it into MGS3's gameplay. As you might expect, crouching can help you better use cover and offers an improved camo index (MGS3's visibility mechanic) compared to standing upright, all while letting you move faster than while prone.
It's some seriously impressive work, and borrowing the 3DS version's animations helps it blend in seamlessly—the mod makes it look like crouch walking was always part of the game. I'm curious how this will affect MGS3's balance though—I know purists tend to snub their noses at the 3DS version's addition of this feature.
There's an argument to be made that MGS3 was built with the limitations of its clunkier controls in mind, and dropping the nimble, Olympic athlete Snakes of later MGS games into this environment can undercut its challenge. I'm more than happy to see the long-suffering players of the MGS Master Collection get more goodies, though, and I could also see this addition helping the nearly 20-year-old MGS3 go down smoother for new players.
Playing MGS3 with crouch walking added may also give us an idea of how the Snake Eater remake, Delta, will feel—that game's first trailers suggest Naked Snake will have access to some of his fancy new moves from later games, like crouch walking, while the environments look like they have the OG layouts (though Konami may surprise us). I just feel bad for Snake's poor knees.