999

999 is the Rayquaza caught by Nina Q during the Delta Episode of Twitch Plays Pokemon Randomized AlphaSapphire. Its nature is Impish while its normal ability is Speed Boost, but upon mega evolution into Mega Rayquaza, it gains the ability Pressure.

Like Stress, the Rayquaza caught before, it was caught during the Delta Episode, displaced a member of the original Urn victory team and went on to become a member of the second Elite Four victory.

Name
His name 999 is identical to Nina's assigned agent number, 999.