Return to Sender (Return 2 Sender in the beta tests) is an Advanced Powercard in Bloons Card Storm. It removes a target Bloon or Monkey and returns it to the owner's hand. It can be used on either player's cards. It removes all stat changes from the selected card, including the Wizard Monkey's scaling Attack Power, The Eternal's scaling health, and bonus ammo from Try this!. Using this card on the opponent while they have a full hand will delete the targeted card entirely. Return to Sender is the only way to have most cards that cannot be put in a deck in the player's hand (e.g. Undead Bloon, Undead MOAB, and Baby Monkey).
The card art depicts Adora, who was not a playable Hero until after the card was released.
Return to Sender can be used to open up a slot for another friendly Monkey, or to add room for a stolen Monkey via Expert Negotiator.
Monkeys with On Play effects can be replayed if removed by Return to Sender. Of these Monkeys, this is best used for Thunder Druid.
If played while the opponent's hand is full, the card will not return. So, for this case, it essentially would be a cheaper Shrink without the Baby Monkey. This is never the case if used on the player's side, because playing Return to Sender would give room to another card anyway.
In the case of The Eternal, Return to Sender against a full hand deletes that Bloon completely.