The ball where all the cats gather in the musical "Cats" is called the Jellicle Ball.
The Jellicle Ball is a pivotal event in the musical "Cats," where the Jellicle Cats come together for a night of celebration and anticipation of the Jellicle Choice, during which one cat is selected for a special journey known as the Jellicle Heaviside Layer. The ball is filled with lively music, dance, and theatrical performances, showcasing the unique personalities of each feline character.