In the magic (blue) catbox you are guaranteed to find a new supercat. These boxes can only be purchased at the store.
On 16 level the new game mode is unlocked – disco mode. The edge of game field becomes covered with a progress bar. This bar is filling up and down during the game. But it becomes filled up faster if you do longer chains more frequently. As soon as whole bar is filled up disco mode becomes active: you gain triple amount of points and goldfish earned by you within next 7 seconds.
Disco mode can be activated by Disco supercat as well.