You can either make a creature tiny or massive, removing a chunky blocker or boosting one of your own attackers
You might draw one when your foe controls no creatures or when you need something else, like a creature of your own
Youll want to have some cheap creatures in play already to validate the reveal condition, so cheap changelings like Three Tree Mascot pull their weight
However, other cards like Teferi, Time Raveler or Supreme Verdict offer more versatile and powerful effects, making it less likely that the Ancient Copper Dragon Card would see play in competitive Magic: the Gathering decks
You feed the cat Humans, he grows, and protects himself
Given their power and popularity, many planeswalkers have received multiple printings and special versions for collectors to chase after