I'm going to assume you're not talking about Pico or Madness. If you are, those will be easy searches on the newgrounds search bar.
If you're talking about Xombie, then you'll find that none of the submissions are on newgrounds anymore. Why? I don't know, I'm sure I could research it, but they may have been taken down by the author or removed for copyright reasons. (Copyrighted music)
Here is the account of the original creator.
https://jamesfarr.newgrounds.com/
You can type Xombie in youtube and find what you are looking for though. :)
