Ai was the deceased daughter of the head scientist that Giovanni hired to create Mewtwo, and was allowing the scientist to try and clone his daughter while he worked with cloning Mew. The scientist thought that if he could successfully create a clone with the remaining Dna of his daughter, (he had managed to contain her "essense" for a while on his own in his basement while his wife walked out on him for all the hurt this was causing) then everything would be alright. When Mewtwo's mind (he's still a baby inside his tank) telepathically connects with the essenses of Ai and clones of squirtle, charmander, and bulbasaur also in the lab, he makes friends. However, it all goes to shit since Ai was too unstable, and the loss of the clones and Ai almost made little Mewtwo go crazy with anger and mentally cause havoc, until he's sedated. He's the only clone out of the 5 to survive. (Sorry for the longwindedness, just wanted to be helpful. Probably just should've set up a wiki link or something.)
