The United Coalition of Arco Iris

 is the eighteenth episode of the third season of Star Teens Unite!.

Summary
Julie's guardian Stella invites every Star Teen, Star Mom, and Little Star Kid for a union meeting in Star Headquarters in Arco Iris where every Star Teen, Star Mom, and Little Star Kid around the world is gathered. But things go wrong when every prehistoric monster from long ago terrorizes Arco Iris! Will they stop them and send them back in time?

Major Events
Arco Iris' union meeting in Star Headquarters.

Characters

 * Ella
 * Inidra
 * Sandra
 * Felicia
 * Lisa
 * Tanya
 * Sheila
 * Julie (Ella's younger sister)
 * Paul (Sandra's younger brother)
 * Antonio (Tanya's younger brother)
 * Maya (Tanya's younger sister)
 * Every Star Teen, Star Mom, and Little Star Kid from around the world
 * Stella
 * Prehistoric monsters

Voice Cast

 * Aimee Carrero - Tanya
 * Alana Ubach - Antonio
 * Ariel Winter - Julie
 * Colleen O'Shaughnessey - Trixie
 * Cree Summer - Heather
 * Grey Griffin - Sandra, Samantha
 * Jessica DiCicco - Stella
 * June Angela - Daphne
 * Kari Wahlgren - Ella
 * Kate Micucci - Inidra
 * Kath Soucie - Paul, Debbie
 * Kimberly Brooks - Sheila
 * Maria Canals Barrera - Elena
 * Nika Futterman - Maya
 * Tara Strong - Felicia, Judith
 * Vyvan Pham - Lisa

Trivia

 * The sixth time that every Star Teen (even normal girls) are masked throughout (even their younger siblings and their moms), the first being Masked in Seattle, Vampira City, The Search for The White Knight, To The Rescue, and Restoring Orlando. Here, at the episode's start, Ella and the girls, their mothers and siblings are perfoming their ritual.
 * Besides the United States, the international members of the Star Teens are from Mexico City, Toronto, Rio De Janeiro, Nassau, Paris, Rome, London, Moscow, Berlin, Dublin, Madrid, Lisbon, Beijing, Tokyo, Singapore, and Sydney.
 * The prehistoric monsters that attacked Arco Iris include Apatosaurus, Allosaurus, Brachiosaurus, Diplodocus, Styracosaurus, Ornithomimus, Trachodon, Tyrannosaurus, Triceratops, Pteranodon, Ankylosaurus, Stegosaurus, Megalosaurus, Iguanodon, Ichthyosaurus, Elasmosaurus, Saber Tooth Tiger, and Woolly Mammoth, all of whose designs are based in their 1970's versions.