FWIW I tried looking a few up and standard library seemed hit-or-miss:

JavaScript it didn't work:

  class testClass {
    constructor() { }
    
    callHoHe() {
      console.log('ho', 'he');
    }
  }

  let hi = new testClass();
  hi.callHoHe();

  testClass.callHoHe = () => {
    console.log('haha');
  }

  let heh = new testClass();
  heh.callHoHe();

This ended up just printing 'ho', 'he' twice,

For Java people didn't think it was possible:

https://stackoverflow.com/questions/47006118/is-there-any-wa...

For Java they said here that you just have to use your own similar implementation.

And for C# they have some pretty intense restrictions on overriding standard library stuff:

https://stackoverflow.com/questions/21302768/where-we-can-ov...

Golang doesn't seem to have this functionality as well:

https://stackoverflow.com/questions/37079225/golang-monkey-p...

Ps. it would have been nice to have monkey patching when dealing with btoa and atob in JavaScript, since they have different function on NodeJS vs the browser.