Body Snatcher

When this creature enters, exile it unless you discard a creature card.
When this creature dies, exile it and return target creature card from your graveyard to the battlefield.

Dominaria Remastered

When Body Snatcher enters the battlefield, exile it unless you discard a creature card.
When Body Snatcher dies, exile it and return target creature card from your graveyard to the battlefield.

The List

Urza's Destiny

When Body Snatcher comes into play, you may choose and discard a creature card from your hand. If you don't, remove Body Snatcher from the game.
When Body Snatcher is put into a graveyard from play, remove Body Snatcher from the game and return target creature card from your graveyard to play.

Although you can choose Body Snatcher itself as the target of its last ability, it will be exiled before it can be returned to the battlefield.

You choose whether to discard a card or not as the enters-the-battlefield ability resolves.