"Stump Day" is the first segment of the Christmas-themed episode of the Disney XD animated series Star vs. the Forces of Evil, produced as part of the show's third season. It premiered alongside its partner episode, "Holiday Spellcial" on December 2, 2017.
The episode begins on Mewni, where everyone is celebrating a wintertime holiday called Stump Day. As the Butterfly and Johansen families celebrate at Butterfly Castle, King River tells the story of the first Stump Day. Long ago, a small group of seafaring explorers crashed their ships on Mewni during a cold winter night. After weeks of traveling together, disagreements arose between them, and they planned on going their separate ways when a harsh blizzard suddenly struck. In order to survive, the group huddled together around a giant tree stump to keep warm and share supplies. A strong bond of friendship was forged between them, and they commemorated the occasion by carving their initials into the back of the stump. Thus, Mewmans come together each year to honor the stump for a full 24 hours "or else".
Star spends the whole day happily honoring the holiday with her loved ones while Marco appears to be planning something. That night, after Star goes to bed, Marco comes to her room to ask for help in closing a window downstairs. However, this turns out to be a ruse to lure Star to her 15th birthday party (a quinceañera with a mariachi band), since her birthday falls on the same day as Stump Day. While Star's friends are thrilled to celebrate her birthday, Star herself is horrified because Stump Day is a day to honor the Stump exclusively. Even though her friends don't believe in the Stump, Star doesn't want to unintentionally anger it by not paying it proper tribute, and she takes down all the party decorations.
When Marco and Tom disagree over whether they should've thrown a party in the first place, Marco accuses Tom of being a bad boyfriend, and they get into a fight. Similarly, Janna and Kelly get into an argument when Janna suggests that Kelly has a crush on Marco, and Tad still refuses to move out of Kelly's hair. As Pony Head and StarFan13 join all the yelling, Star fears angering the Stump further and opens the windows to let in the cold and recreate the weather conditions of the first Stump Day. However, her friends still don't believe in the Stump, and Janna throws a ceremonial stump in the fireplace to keep warm.
All of a sudden, the lights go out, and monstrous tree roots invade the castle. The Stump (which turns out to be a real, vengeful creature) appears to capture Star and her friends. When King and Queen Butterfly enter to see what's going on, the Stump captures them as well for being non-believers. Star's friends apologize to her for not believing in the Stump and ruining the holiday, and Star forgives them. They join hands and come to grips with their imminent deaths, but the Stump suddenly vanishes and the lights turn back on. Marco believes the Stump spared their lives because they came together in friendship and love, but Star says it's because it's past midnight and Stump Day is technically over.
Even though the Stump was about to kill them, Star gives thanks to the Stump for helping them come together in the end. King and Queen Butterfly decide to have a bigger Stump Day celebration next year just to make sure the Stump isn't angered. Star thanks Marco for throwing her a surprise party, and with her approval, the group dances together to mariachi music.