Killer Bunnies games can be expanded by adding Booster Decks. Each booster deck adds more cards (with a new back color) to the game, and most of them add new concepts as well. It’s best to add booster decks in order, since some cards in later booster decks will be useless if the game doesn’t have a certain card from an earlier booster deck. Sometimes earlier cards will refer to other cards in later booster decks, but not in a way that makes them useless.
When adding a booster deck, combine its cards with the similar cards already in the game and shuffle the new boosted deck. Cards with the sinister bunny on the back go with the other sinister-bunny-backed cards, cabbage and water cards with the other cabbage and water cards, and so on. Starter cards and carrots with the timid bunny on the back do not need to be shuffled but should be joined with the other timid-bunny-backed cards.
The Quest for the Magic Carrot starts with the Blue Starter Deck and includes the Yellow Booster Deck, which is the first booster for that game. The other decks should be added in order, except for the Chocolate Booster Deck which can be added at any time.