Spoiler Alert!!! (Contains info about the Pokemon delta episode).
I was recently playing the delta episode of Pokemon Alpha sapphire and I was trying to catch Deoxys. However, my Pokemon kept knocking it out (due to critical hits), forcing me to restart the process of catching both Rayquaza and Deoxys (since the game will not let me save between the battles). So I had to restart about four times and every time I tried to catch Rayquaza, all I had to do was get it into red health or put it to sleep (with green health) and use an ultra ball to catch it. (I also recall catching it in a PokéBall with green health the first time I caught it.) But according to every Pokemon Rayquaza page, its catch rate is 3 (0.4% with PokéBall, full HP), which is really low. I am wondering if I was just super lucky or if the catch rate for the Rayquaza in the delta episode has a higher catch rate then normal.