A: It’s pretty much whatever you think makes sense, and everyone can agree on. If you think you might want to combine these decks again, you might write down your decisions (and maybe rate how well they worked, just in case they… didn’t)

Does it make sense for the Witches from Monster Fluxx to have the powers of a Spellcaster in Fantasy Fluxx?

Does it make sense that the Martian Zookeeper (Goal) in Martian Fluxx would accept a Parrot or Monkey from Pirate Fluxx in place of the Cow?

Does it make sense that the Knights of Ni might accept Trees in place of A Shrubbery?

Is the Pirate Fluxx Parrot sufficiently relaxed to stand in for a Resting Parrot in Monty Python Fluxx?

Should the Dragon from Fantasy Fluxx be given the “Monster” designation if combining with Monster Fluxx?

It’s all up to you… but, as with any House Rules, make sure you get it all clear and agreed upon BEFORE you start the game!