Star must fight off Ludo and his army of monsters when they crash Brittney Wong's birthday party.
Star is enjoying getting the admiration of her fellow students who all either want to befriend her or get noticed by her. She suddenly spots Brittney passing invitations to her party, as well as skipping over those she deems unworthy or not cool enough. When Star asks if she can come, Brittney outright insults her saying that the only way she will come is if pigs fly, which Star obliges with. She gets prepared and brings Marco along to Brittney's party bus, which zooms past their house. Blasting themselves onto the bus, Buff Frog watches from a distance to report back to Ludo. The party attendees are shown to already be annoyed with Brittney's obnoxious and rude behavior until Star and Marco burst in; exciting everyone. Marco notices that Jackie-Lynn is at the party and tries to make himself look good, but has trouble as he gets motion sickness.
Star begins to realize that Brittney may have been sarcastically teasing her, so she tries to make the best of it when the bus gets stalled in a traffic jam. She conjures a laser puppy to spell "Happy Birthday, Brittney," turns the interior into a bounce house and creates a clam shell hot tub on the roof of the bus (exciting everyone, but making Marco sicker). Brittney the whole time refuses to be excited for any of it, declaring the party a disaster and making Star feel depressed. At the next bus stop, Brittney demands that Star and Marco leave, which they do, only to be welcomed by Ludo and his minions who force them back onto the bus for a fight, with Three-Eyed Potato Baby taking over the wheel and speeding the bus towards a portal.
Star and a motion sick Marco attempt to fight off the minions while Ludo and Brittney bond over their mutual hatred of Star. Eventually, Marco knocks out Potato Baby and spins the wheel with the bus flipping and crashing. All of the party attendees miraculously leave unharmed while all the monsters are injured. Marco finally vomits into a trash can with Ludo joining him after he ate a whole plate of bad oysters. Brittney immediately accuses Star of ruining her party, but the rest of the party goers voice their approval to her which only seems to annoy her. Marco congratulates Star adding that he would like her to plan his party sometime.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Alan Tudyk as Ludo
- Minae Noji as Brittney Wong
- Grey DeLisle as Jackie-Lynn Thomas
- Daron Nefcy as Sabrina Backintosh, StarFan13
- Jeff Bennett as Justin
- The promotional poster featured a different title, "Party Bus", instead of it being the original title.
- Brittney is revealed to be a terrible singer in this episode.
- It is revealed that Marco gets motion sickness in this episode.
- While eating oysters, Ludo says, "There's a rumbly in my tumbly", a reference to a song "Rumbly in My Tumbly", in Disney's Winnie the Pooh and the Honey Tree.
- Star's backpack in this episode looks similar to the infamous Spiny Shell (also known as Blue Shell) item from the Mario Kart games (specifically starting in Mario Kart 64).
- This is the last episode to be animated by Mercury Filmworks.
- May 3, 2015 (Canada)
- May 14, 2015 (United Kingdom and Ireland)
- July 30, 2015 (Germany)
- August 10, 2015 (Australia)
- September 6, 2015 (Israel)
- October 9, 2015 (Turkey)
- October 23, 2015 (Poland)
- November 5, 2015 (Spain)
- December 6, 2015 (Southeast Asia)
- January 29, 2016 (Japan)