Spike: I'm hungry, can you give me some of those gems?
Rarity: No, Spike! I'll use these for jewelry and dresses!.
*Rarity walks to her house*
Rarity: Now time to make a beautiful dress!
*Lets the gems down*
*Suddenly, the 3 ran away from Rarity's house*
Rarity: Why are these gemstones running away! They can't even walk!
*A few rough hours later, Rarity became insane and poofed the gems. She then started working on a dress for somepony*
Rarity: Finally, they'll stay here, forever..... *Laughs manically*
*Rarity falls alseep*
*Suddenly, Spike appears and eats Amethyst's gem and Sapphire's gem, then he leaves*
Unlikely since they're owned by two different networks. It would have made more sense to do an Adventure Time crossover since that would put two of Cartoon Network's top rated shows together that are currently running.