"The Classroom Gems: Fusion" (referred to as "The Classroom Gems: Special Lesson" in the title card) is a Classroom Gems short.
Video can be watched here.
The episode starts with Garnet punching the title card and yells that she's going to teach the viewers about fusion, thus unfusing into Ruby and Sapphire. Next, Pearl explains about fusion, while the four perform separate fusion dances: Ruby and Sapphire fuse back into Garnet, and Pearl and Amethyst fuse into Opal. Garnet explains further, as Opal loses her balance and unfuses back to Pearl and Amethyst. An irked Pearl berates Amethyst for not collaborating, but Amethyst retorts, doubting Pearl's collaboration. Garnet then shows a clip of the several fusions throughout the show, including Sugilite and Stevonnie. Steven interrupts with a question asking what the main purpose of fusion is. With Garnet's prompt, the Crystal Gems subsequently fuse into Alexandrite, pose, and answer with "Love!" The episode ends with a title card saying "Class Dismissed"
- Opal (non-speaking cameo and on screen)
- Ruby (non-speaking cameo)
- Sapphire (non-speaking cameo)
- Alexandrite (cameo and on screen)
- Sugilite (on screen)
- Stevonnie (on screen)
- Greg (on screen)
- Chalk Board
- Dance Studio
- Neither Opal nor Alexandrite had their new regeneration outfits, despite Amethyst and Garnet already having reformed; this could be intentional to avoid spoilers.
- When the 3 Gems fuse into Alexandrite, she makes a pose with a background similar to that of the Powerpuff Girls franchise, where a heart background is seen with the girls posing at the end of each episode.
- The short, as well as "How are Gems Made?" and "What are Gems?", is a homage to the Gunbuster OVA called "Science Lessons".
- While Garnet was fusing, Ruby and Sapphire's gems switch.
- Garnet's/Ruby and Sapphire's gemstones on Alexandrite are on the bottom set of arms instead of the top ones.
- However, there is no rule stating that multi-limbed fusions need to keep their gemstones on the same pair of limbs after every regeneration/re-fusion.
- When fusing into Alexandrite, Amethyst's Gem goes where Ruby's should be, while Ruby's goes where Amethyst's should be.
- Despite all the gems appearing to look "chibi", Steven is the only Gem who didn't retain this appearance from the previous lessons.
- When Amethyst and Pearl fuse into Opal, despite having their new regenerated forms, she has her debut outfit.
View the episode's transcript here.