As long as Light Arcanine is your Active Pokémon, once during your turn (before your attack), if your opponent has any Benched Pokémon, he or she chooses 1 of them and switches it with the Defending Pokémon. This power can't be used while Light Arcanine is Asleep, Confused, or Paralyzed.
If the Defending Pokémon is a Baby Pokémon, this attack does 10 damage instead of 50. If the Defending Pokémon is a Basic Pokémon, this attack does 30 damage instead of 50.