Oola

 Oola is the secret language that Francine, Muffy and Sue Ellen use in Do You Speak George. It was taught to Francine by Catherine. Since Francine refuses to teach Oola to Arthur and Buster, they invent Arster-Buthur instead.

 Oola is a version of pig latin.

Rules
 First, all consonants before the first vowel are moved to the end of the word.

 Then "oola" is added. (Other versions of pig latin may add other syllables.)

Examples
what -> atwh -> atwhoola

 marble -> arblem -> arblemoola

 Francine -> Ancinefr -> Ancinefroola

Trivia
Languages like Oola are usually spoken rather than written. When writing some Oola words you either have to bend English pronunciation rules or change the spelling. For "what" you might want to write "otwhoola" rather than "atwhoola" so that people will not pronounce it "ettwhoola".

Appearances
Do You Speak George?  100901