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 625 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" that were given to them by Jumba and Pleakley. Lilo names the two experiments Yin and Yang and repurposes them to create a new island.
- In one scene, Reuben is shown with four toes on each foot, even though he normally has only three toes per foot.
- Moral: We accomplish more working together than working against each other.
- 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, although it is later revealed that he had fallen asleep while in the middle of reading.
- Yang is the only experiment besides Stitch to escape a net by himself.
- Though Yin apparently has no visible 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.
- When Jumba and Pleakley are dancing the 1,000-hour-long Gloknar, the tune is played to the song "Play That Funky Music" by Wild Cherry, except with changed lyrics.
- Jess Winfield, one of the show's executive producers and screenwriters, stated in 2004 on his TV Tome (today TV.com) thread that "Yin-Yang" was his favorite episode of the series, saying that he liked the experiments, story, and theme.
- L&S Says Mahalo. TV Tome (December 13, 2004). Archived from the original on March 19, 2016. Retrieved on May 27, 2018. “Favorite episode: "Yinyang." [''sic''] Two cool experiments, a good Lilo and Stitch story, and the episode's theme all work really well together. Other faves: "Angel" and "Bonnie and Clyde."”