This is the strongest and most deadly enemy in the Empire of Cats Chapters. It is first seen in Chapter 3-48, known as the Moon (Chapter 3-48) in the English version. Some Stories of Legend levels will also have Teacher Bun Bun and his colored variants. He has a massive 399,996 HP (that's nearly 1/2 of the Moon's base) and 9,000 damage in Chapter 3 - Moon. Some say he is impossible to defeat, but he can be defeated with the proper strategy, an example being a continuous "meatshield" spam (e.g Basic Cat,Tank Cat, or Boogie Cat).
Also is easily countered by numerous Paris Cats and Dragon Cat stacks, with proper meat shield spamming.
So a lot of people fall into the trap of spending catfood in order to defeat bun bun when they first encounter him. Although bun bun is the hardest boss in EOC, with proper strategy and linesups, you can defeat him without spending any catfood.
Before attempting, it is highly advised to have 100% treasures or at the very least, activate them. Save your catfood since you might regret spending it later. Patience and being rational is the key to winning. Plus, there will be much harder challenges to overcome in the future.
Summon a Valkryie Cat and use cats to protect her.
Upgrade your Worker Cat to max, then get a full wallet.
If you are close to the enemy base, stop spamming cats.
Once you have money, summon every strong cat you have.
When Teacher Bun Bun comes out, deploy every cat you have (you should have at least 3-4 meatshields).
Call God for knockback if Teacher Bun Bun is close to your ranged attackers.
You should win if you have good cats; Congratulations!
Strategy for late game encounters
For now, you should have more anti-Floating units in your arsenal that can help you. Strong units like Catman and stacks of heavy hitters like Dragon Cat or Paris Cat can deal enough damage to knock him back and prevent him from attacking your long-range units, or units with slow/freeze abilities can greatly help to win against him. Megidora is very helpful against him and his variants, as his knockback ability can prevent him from getting close to your heavy hitters, and his slow ability can keep your line safe. Kai can also tank many hits from him (especially in True Form), and deal heavy damage if she gets close enough to attack him.
Former Master of Teacher Bear. His physical punishment is love. Don't think. FEEL!
Excluding the Mega Cat and Beefcake Cat event enemies, Teacher Bun Bun has the highest money drop in the game; 8000 with Level 1 Accounting and no Treasures!
This enemy's money drop is so high,that it'll always fill up the player's wallet completely.
Teacher Bun Bun is the only enemy boss that doesn't has a variant in annual events as well as collaboration events (like The Face - Princess Head).
According to Li'l Bun Bun's description about the Grand Prix, he is very likely a reference to Bowser, antagonist in the Super Mario Bros. franchise, especially the very similar arm details, plus both being an iconic enemy.
Teacher Bun Bun is never fought at 100% magnification.
Teacher Bun Bun used to be Floating/White-type, but it was changed to just Floating in update 5.10, when Shadow Gao was released.