Neither Wash nor Rarity will ask for a rare one right off the bat - Wash figures there are better people to get one, and Rarity doesn't think she needs one, as Spike is certainly doing a good job of protecting her.

That said, Wash will talk to whoever gets the Frootz Cat and try to trade them the pieces he still has left over from the Moogle Party (Ursa Circus or Kab Kannon) in exchange for the cat. (Somebody has wanted a pink fruity cat for a while, okay.)