"Cornball!" is the first segment of the sixty-sixth episode of Star vs. the Forces of Evil. It premiered on April 7, 2019 alongside "Meteora's Lesson", and is the first segment of the tenth episode in the fourth season.
Star tries to convince Buff Frog to move back to Mewni.
Mewni is putting on a Cornball match between Mewmans and Monsters; making it the first ever pair up in history. Star invites Buff Frog and his children to the game in an effort to convince him to stay in Mewni. Buff Frog does not think that Mewmans and Monsters will accept each other as their differences are too vast to reach any understanding. Regardless, his children, especially Katrina his youngest, are optimistic and just glad to be with Star again. Meanwhile, Eclipsa is looking all over for Meteora who keeps wandering off and causing a mess and up in the announcer's office, Marco and Kelly make the call even though the former has no idea how the game works. Kelly goes to get snacks, leaving Marco to look over the extensive rule book.
Things immediately get off to a bad start when the players pick their team members; the Mewmans pick Mewmans and the Monsters pick Monsters. Star gets furious at this as she planned the event for integration. They sarcastically "mix it up", but only go back to their segregated teams. Star attempts to rouse the audience by telling them how much they all equally love Cornball, but this only causes both sides to announce their superiority over the other. Buff Frog views this as a sign that Mewmans and Monsters will never coexist. All the children, who have grown bored by the arguing, all sneak off to enjoy themselves.
As Star, Buff Frog and Eclipsa, realize that the kids are missing, they learn through two of Buff Frog's lingering kids that they have all gathered in the back to have their own Cornball game. Everyone rushes outside to see exactly what Star wanted: Mewmans and Monsters integrating. Marco learns the rules just in time to announce the game with Kelly eventually coming around to join him. The game ultimately ends with a victor and everyone celebrates, though the adults still give in to minor squabbling. While Star is disappointed that everyone is still angry, Buff Frog tells her not to worry because the younger generation will fix the old one's mistakes and opts to stay in Mewni.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Fred Tatasciore as Buff Frog
- Kimaya Thais as Katrina
- Dana Davis as Kelly
- Esmé Bianco as Eclipsa Butterfly
- Kari Wahlgren as Meteora Butterfly
- It is revealed that sports and playing fields exist on Mewni, despite Star being unaware of them in "School Spirit".
- Buff Frog's tadpoles have developed into nearly fully-grown frog monsters by this episode.
- Kelly and Marco still refer to each other as breakup buddies after "Kelly's World".
- June 14, 2019 (Southeast Asia)