"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 "Spider With a Top ", and is the second segment of the tenth episode in the second season.
Worried about his tadpoles’ futures, Buff Frog investigates the hole in the Mewman force field.
- 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)