Ditto Pokemon Power Transform
When using the Base Set Ditto as my active pokemon, his only option is to use the transform pokemon power. Is this power always in effect or can I choose not to use it?
For instance, suppose I defeat a Base Set Charizard, but take 40 damage in the process. After this, my opponent switches in a Base Set Rattata with 30HP. If the pokemon power is always in effect, Ditto should be knocked out when Rattata is switched in because he will have more than 30HP. Is there any way to avoid this by not using the pokemon power at any time in the gameplay?