Transform can change many features of the Pokémon temporarily. The features are as follows;
- Pokémon Species
- Pokémon Cry
- Attack Stat
- Defense Stat
- Speed Stat
- Special Attack Stat
- Special Defense Stat
- Stat Changes
- EXP Yield
- Pokémon Moves
As such, this means that apart from its HitPoints and Level, Ditto/Mew is essentially the other Pokémon. Also, the EV training that you have put on Ditto becomes void for this battle. However, that said, when Critical Hits happen, it will still be based upon Ditto/Mew's stats. As the Pokémon's catch rate changes, if you wish to capture a Ditto or a Mew (Level 30 in Emerald will know Transform, although it isn't too likely to use it) with greater ease, then send in a Pokémon with a high capture rate such as Magikarp in battle first and then it should be very simple to capture. Its EXP Yield also changes so the EXP gained from beating a Ditto depends upon the Pokémon it has transformed into. Ditto can Dynamax after Transform if the PokĂ©mon it transformed into can Dynamax. So Ditto when transformed into Zacian, Zamazenta or Eternatus cannot Dynamax |