Migrate to movies se if need be please.
It says in this reddit post here
TIL Francesca Marie Smith, the voice of Helga from Hey Arnold, actually started writing episodes of Hey Arnold when she was only 11 years old. She wrote a total of 10 episodes.
There's a link to the wikipedia page, but I couldn't see any indication that she was a writer for HA!. However, she is credited as doing such on IMDB. Any source for the IMDB thing?