What is the Comeback Kid Power-Up?

How do Power-Ups work? What are the different types of Power-Ups? How do I read a Power-Up card? What power-ups are available? How do I know what and how many power-ups are available in an activity? Why am I hearing sounds when I fire a power-up? What are Abilities? What is the Attack Dog Power-Up? What is the Corner Caper Power-Up? What is the Great Responsibility Power-Up? and 7 more ...