"Is Mystery" is the second segment of the twenty-third episode of Star vs. the Forces of Evil. It premiered on October 3, 2016 alongside "Friendenemies", and is the second segment of the tenth episode in the second season.
Buff Frog attempts to solve a mystery of a hole in the wall guarding the cornfield when he gets captured by Meat Fork, a humanoid warthog monster with a fork for a left hand. Upon being put to work to grind corn, Buff Frog frees himself to discover who is enslaving the monsters. He encounters the rats as well as Ludo, who offers him Meat Fork's job. Buff Frog refuses and escapes with Meat Fork. Buff Frog decides he will warn Star that Ludo is back.
- Star Butterfly and Marco Diaz are both completely absent for the first time, but Star is mentioned by Buff Frog at the end of the episode.
- October 27, 2016 (United Kingdom and Ireland)
- November 18, 2016 (Italy)
- January 13, 2017 (Poland)
- February 12, 2017 (Japan)
- March 8, 2017 (Latin America)
- April 21, 2017 (Southeast Asia)