Trying to remember the name of a book.

[Nan]

This reminds me. I'm trying to remember the name of a cartoon I used to watch.

There was a blond girl and two boys and a monster. I think they hung out in a treehouse. The monster was a good monster but at some point goes back to "monster land."

I figure it's from the 80s.

Edit: Ahh. Never mind. Found it. "My Pet Monster."