Mewtwo is a catch rate of 3. Just because you happened to catch it with only a couple Ultra Balls does not mean a catch rate is really high.
cardgjammer said:I have caught almost all my pokemon on first try in my Y(my only escapees are those that came while I had less than three poke balls left). I don't know why, but I do know of the oldest trick in the capture book that people used to mention to refer to how they caught pokemon in the old safari zone, where the "rock, bait, ball, run" menu is seen: the A-button-and-timing trick... May not be known to work now, but given my luck by mashing A with timing, I'm not so sure how to explain it in terms of whether or not it still works... But until people discover, in their perspective, that it works for them, I'll take it with a salt grain and not recommend or deny that it works while leaning towards trying it to exercise my hands, although it may not work in terms of actually catching it...