Rotting Rats — ruling 1

When Rotting Rats's "enters" ability resolves, first the player whose turn it is chooses a card to discard, then each other player in turn order does the same, then all cards are discarded at the same time. No one sees what the other players are discarding before deciding which card to discard.

Rotting Rats : règles, fonctionnement et interactions (MTG)

Rotting Rats is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this creature enters, each player discards a card. Unearth (: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

How it works : Rotting Rats

Original English text — Wizards of the Coast / Scryfall

#1February 1, 2009· Wizards of the Coast
When Rotting Rats's "enters" ability resolves, first the player whose turn it is chooses a card to discard, then each other player in turn order does the same, then all cards are discarded at the same time. No one sees what the other players are discarding before deciding which card to discard.
No other card is named in this ruling.