Scrat's epic pursuit of his elusive acorn catapults him outside of Earth, where he accidentally sets off a series of cosmic events that transform and threaten the planet. To save themselves from peril, Manny, Sid, Diego, and the rest of the herd leave their home and embark on a quest full of thrills and spills, high and lows, laughter and adventure while traveling to exotic new lands and encountering a host of colorful new characters as well as a new enemy who is a brother to one of their old foes.
Star Butterfly is a magical princess from the dimension of Mewni. On her 14th birthday, she receives the family heirloom wand. After she accidentally sets fire to her castle, her parents decide that a safer option is to send her to Earth as a foreign exchange student. She befriends Marco Diaz and lives with his family while attending Echo Creek Academy. Star and Marco must deal with everyday school life while protecting Star's wand from falling into the hands of Ludo, a villain from Mewni who commands an army of monsters. Star and the folks from Mewni are able to travel across dimensions using "dimensional scissors" that can open portals.