Gooble Goble is chanted when a group of freaks make a norn "one of them", such as when a norm gets married to a freak. Comes from the movie 'Freaks'.
The term has been used in South park and Doctor Phineas Steel song 'Donkey Town'.
"Gooble Goble, Gooble Goble, One of us! One of us!" - Freaks
"You will be on of us! Gooble Goble, Gooble Goble!" - Doctor Steel