Yeah I've seen some of that language manipulation. I guess my question is, does this happen in Forth regularly or not?

In JS you can manipulate the prototype for a data type but unless you're making some sort of library for a new type of framework most developers never do that type of stuff. In Ruby duck typing is the idiomatic way to solve many problems. In Lisp the use of macros is fairly common that a good majority of larger projects use. Not sure if that type of lower level manipulation is something everyone does in Forth or just something possible.