When she first appears in "Mewtwo Returns", Domino seems to be a nice person. Brock automatically falls for her (at least for a few seconds). She works a "cover" job at the Pokemon Institute, but is secretly a Team Rocket elite member. She uses a fake valley-girl voice at first (sounding almost like one of Misty's sisters), acting like a little cheerleader.
But then, her true personality was revealed as Agent 009, Domino, also called "The Black Tulip". As she says, "A friendly face can hide the fiercest foe... you just never know!" Having no patience for the antics of Jessie and James, she pops their balloon with one of her black tulips and glides straight to Giovanni's helicopter.
Once Domino and the Team Rocket air strike squad land at Mewtwo's home, she instantly scoops one of the adorable baby Nidoqueen into her arms, showing her affinity for "cute" Pokemon. However, she has no sympathy for the injured clone Pokemon, or Ash's Pikachu, as she captures Ash-tachi, the researchers, and all the clones. She then sets Jessie and James to work, making them scrub the floors "until I can see my face in there!"
Jessie and James get their revenge on Domino when she's fleeing from
the angry Bug Pokemon. As the elite Rocket slips on the newly-waxed floor,
landing with her head in a bucket, they quip:
After the Bug Pokemon put all the Rocket grunts to sleep, Mewtwo moves the lake underneath the surface of the crater, protecting the sacred waters from further harm. Although Ash, Misty, Brock, Pikachu, Jessie, James, Meowth, and the clones keep their memories of what just happened, Giovanni, Domino, and the Rocket minions have their memories erased. At the end, Giovanni is left feeling confused, but "utterly defeated", as he, Domino, and the air strike squad hurry back to HQ.
More information about Domino is unknown at this point. It is unknown whether she'll return to the series again, but she is certainly an interesting character!