There's already a Pluto mold from the Fabuland Mickey Mouse sets from the early 2000's. He may be a bit big for an accessory, but I'd think this would be worth a minfig slot.
Just picked up a complete set at a local Target in Missouri. Only had one duplicate (Nelson), but I was able to quickly find a Milhouse to complete the set. These figures are a ton easier to ID through the touch method than all previous series.