"Yin-Yang" is the ninth episode of Lilo & Stitch: The Series. It aired on October 17, 2003.
Two experiments activate at the same time while Lilo and Stitch are arguing. Lilo and Stitch insist that they each can catch an experiment without the other. Meanwhile, Jumba and Pleakley make a bet to see which one will capture an experiment first, and Gantu forces Reuben to help him catch them both. The race is on because Jumba theorizes that the world will be doomed if the two elementally opposing experiments touch each other, they will destroy Earth. Eventually, Lilo and Stitch team up together again and help each other capture the experiments each was after using the "tools" given to them by Jumba and Pleakley. Lilo names the two experiments Yin and Yang and repurposes them to create a new island.
- Moral: We accomplish more working together than working against each other.
- Although Yin is female and Yang is male, Lilo erroneously referred to Yin as a male.
- Both of their names are derived from the concept of Yin and Yang.
- Reuben was reading a book titled Escape from Sandwich Mountain, an allusion to Disney's 1975 movie Escape to Witch Mountain.
- Yang is the only experiment besides Stitch to escape a net by himself.
- Though Yin apparently has no mouth, a mouth is seen on her in "Angel" when she and other experiments carry Stitch out of a ship. A mouth also appears on Yin in a few scenes of "Slugger", especially during Lilo and Mertle's argument over the game rematch.
- In spring 2004, Disney Channel held an online poll that asked viewers for their favorite experiments and episodes from Season 1 of the series. According to the top 10 results of that poll, this episode and the titular experiments were #7 on the list.