PRINCESS KARAOKE (Episode 25)

Tai, Joe and their Digimon companions track Mimi to a gigantic fortress where she's being treated like a princess by frog-like beings called Gekomon. 
  

The Gekomon are convinced that only Mimi's singing can awaken their master, ShogunGekomon.  Mimi strings them along, never quite awakening the sleeping giant. 

When Tai and Joe call her a spoiled brat she has them all thrown into a dungeon.  Finally, in a nightmare, Mimi sees what she's become.  She begs everyone's forgiveness and awakens ShogunGekomon, a destructive behemoth who was better left in a coma. 

It takes an appearance by MetalGreymon to put the brute back to sleep.