They'll contain three common cards, two uncommons, one 'wildcard' of any rarity, and a seventh card that may be "a land, a traditional foil, or a Special Guests card"
Theres a pretty popular online tool for this, the Meyerweb reset (which you can find here
When when you crew it, which takes four power, exactly equal to the power of those Cat tokens, you can start copying tokens of any type
Also great stats and trample, which helps a lot with combat damage to a player
This card can easily patch up any holes in a green decks strategy, allowing you to field huge threats each turn while keeping your hand fully restocked with each play
The first generation of players latched onto the dramatic artwork and game-ending power of Serra Angel and Shivan Dragon a pattern which was then repeated around other giant creatures for the best part of three decades