Despite there being no official implementation of the popular Breaking Bad characters into MultiVersus, plenty of creative fans have made mods for you to add to your own game, allowing you to bring Walter, Jesse, and even Gus into the game.
Currently, there’s a mod that will overwrite the design for Shaggy, replacing it with a Walter White rendition to give players a temporary fix to their demands. Unfortunately, the new Walter is not accurately voiced, like the other characters are.
Source: https://www.distractify.com/p/will-walter-white-be-in-multiversus