Cherry Blossom Ghost appeared in "Memory of a Memory" when Ash showed Marceline the Cherry Blossom Wand he had. Ash trades Marceline's teddy bear Hambo— her favorite thing in the world—to get the funds to buy it. When she gets upset at him he remarks that the fact that it was her favorite thing in the world was what made it so valuable. As Maja states, the potent psychic resonance that comes from the amount a person treasures a certain possession is what made Hambo so valuable.
The Ghost that is bound into the wand is similar to any other normal ghost, but he has blue-gray skin.
You're not... a genius... you're not... a genius.