If an attack does damage to Misty's Tentacruel while it's your Active Pokémon, you may switch it with 1 of your Benched Pokémon, which prevents all other effects of that attack on Misty's Tentacruel. This power can't be used if Misty's Tentacruel is already affected by a Special Condition.

Flip a coin. If heads, the Defending Pokémon is now Poisoned. If tails, the Defending Pokémon is now Confused.