Why does Dib sound like his voice has been digitally altered in Invader Zim?

Why does Dib, from Invader Zim, sound like his voice has been digitally altered? Mostly it just makes him sound muffled, but it's particularly obvious in the line, "You're a hideous blob of stolen organs!" in Season 1, Episode 4, "Dark Harvest".

Invader Zim is the love child of a megalomaniac and executive meddling. J.V. visión for the show is incredibly dark for what is supposed to be a children's show, and Nick couldn't commit to it. Because of that, Vasquez was forced to edit and re edit and change and rewrite many episodes, or Nick changed them afterwards.

The result is many jokes are dropped, and lines were redubbed all the time to make them kid safe. That was not the original line, as you can hear.