"Princess Quasar Caterpillar and the Magic Bell" is the first segment of the sixty-fifth episode of Star vs. the Forces of Evil. It premiered on April 7, 2019 alongside "Ghost of Butterfly Castle", and is the first segment of the ninth episode in the fourth season.
After being sent back to the void by his new nemesis, Princess Quasar Caterpillar, Ludo realizes he has fallen into his old ways again. He is confronted by Dennis, Eagle, and Spider, who try to help him. Unfortunately for Ludo, this involves reuniting him with his former henchmen and rebuilding his old castle. When he hears Star's Wand is now in Eclipsa's possession, he finally snaps as he begins scheming on stealing it and openly tells Dennis he hates the castle. As a distraught Dennis turns to leave, he is confronted by the castle's landowner, who reveals he tricked him into rebuilding it for him. Realizing how Denis has tried to help him, Ludo steals the deed to the castle and continues the reconstruction with his brother, and their other siblings.
- June 7, 2019 (Southeast Asia)