- Idling while will not trigger AFK measures.
- The icon for Teamfight Tactics item , which is named after her. is reused for the
- The visual goals for Yuumi included creating a cute support due to having not done one in quite some time.
- A scrapped name for  was Protecc/Attacc.
- Yuumi's in development name was Catbook.
-  was a spell originally tested on and , when one of them died their spirit would attach to the other and would allow you to keep playing.
- Yuumi is voiced by Cassandra Lee Morris who also voices  .
- Yuumi's prototype model was a recolored .
-  prototype particle was a cat from one of skins.
- Several scrapped spells tested on Yuumi include:
- A miniature version of .
- A version of her ultimate that allowed her to attach to enemies and knock them back until they hit terrain.
- A version of that would charge for a second and then fire at an incredibly fast speed.
- A spell that would throw a boomerang like orb that would allow Yuumi to cast her spells from the projectile.
- Yuumi is a magical cat familiar to a Yordle Enchantress named Norra.
- Yuumi's name came from when she heard Norra say  , and thought that was her name.
- Bandle City. was originally written by a Yordle anthropologist in order to study how Yordle magic works and how Yordles traverse the spirit realm. It has been added over the years by generations of Yordle mages who explored the various gateways to and from
- The Book of Thresholds was given sentience by one of its previous owners in order to protect itself from those who would use its powers for evil.
- Yuumi and Book have been looking for Norra for around 4 years.
- Yuumi bears a striking resemblance, both appearance- and functionwise, to the Keystone rune.
- Her splash art shows Yuumi inside Master Norra's house in Bandle City.
- Yuumi's tail works as a rudder for steering book.
- This skin shares the Battle Academia theme with:
- This skin is likely a reference to from the series.
- This skin shares the Heartbreakers theme with:
- She shares her splash art with .
- and can be seen in the background of their splash art.
- Each of her chromas gives her different fur color and patterns that are based on real cat breeds.
- When Yuumi , drawings of and can be seen on pages.
- When Yuumi uses several images can be seen on the ground. All of these reference Heartbreakers skins, such as:
- and have become fast friends, united by their love for Norra.
- It is stated on her Universe page that Bandle City as Norra's familiar (or as a guide). (or ) has relations with , , and , possibly during the time in
- During their travels, Yuumi and Book have encountered . Yuumi rested on his shoulders for a time, protecting him from angry snow-spirits stirring up flurries in a hailstorm, while he brought her wriggling fish.
- Yuumi and Book were attacked by Shurima. while they were investigating ruins in
- ↑ Danky on Yuumi's Visuals
- ↑ Scrapped Bop 'n' Blok Name
- ↑ Yuumi in Development Name
- ↑ EndlessPillows on Yuumi’s Gameplay Hook
- ↑ Yuumi's Voice Actress
- ↑ Prototype Yuumi Model
- ↑ Maxw3ll on Prototype Spell
- ↑ Scrapped Yuumi Spells 1
- ↑ Scrapped Yuumi Spells 2
- ↑ Yuumi's Name
- ↑ Jellbug on the origin of the Book of Thresholds
- ↑ Jellbug on the Book's Sentience 1
- ↑ Jellbug on the Book's Sentience 2
- ↑ Jellbug on how long Norra has been missing
- ↑ Earp on Yuumi's Tail
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