Some things that have to be noted for those that use a combination of fire and ice attacks on castform. First of all, in sunny weather, all chances of inflicting freezing status get reduced to 0% and all frozen pokémon immediately thaw out, in other words, get out the sun and you can't annoy your foes with the freezing status anymore. Secondly, hitting a frozen pokémon with a fire move also automatically cures its freezing status. This can be used by your opponent, switching in their pokémon you froze earlier as they anticipate your fire blast coming in, to be able to move again.
Master balls are the cheapest thing ever invented. It's more fun catching everything with balls that can fail. 'caught Latios in the wild without master ball ftw'