This video shows all Cuphead Bosses that have a secret phase, both in the base game and "A Delicious Last Course" DLC. This includes The Root Pack, Djimmi the Great, Sally Stageplay and The Howling Aces. There's also a secret Devil and Angel Boss fight that can be unlocked at the tombstones on isle IV.

Cuphead is a classic run and gun action game heavily focused on boss battles. Inspired by cartoons of the 1930s, the visuals and audio are painstakingly created with the same techniques of the era, i.e. traditional hand drawn cel animation, watercolor backgrounds, and original jazz recordings.

00:00 The Root Pack
01:12 Djimmi the Great
03:21 Sally Stageplay
05:32 The Howling Aces
08:20 Devil and Angel