If you cast Catch of the Day, you don’t make any choices until it resolves. Opponents won’t know what it is until you serve it up! Once it leaves the battlefield, it forgets the choices you made.

If an object on the battlefield becomes a copy of Catch of the Day, it’ll copy the values chosen for Catch of the Day’s enters-the-battlefield replacement effect.

If an object enters the battlefield as a copy of Catch of the Day, it copies the values chosen previously for Catch of the Day’s enters-the-battlefield replacement effect. However, as the copy enters, it’ll also apply Catch of the Day’s replacement effect again, allowing the copy’s controller to choose an option for Keyword, Whenever this creature attacks, and Size. The newly chosen Size will overwrite the original Catch of the Day’s power and toughness, but the newly chosen Keyword and Whenever this creature attacks abilities will be added on top of any copied abilities. For example, this can cause you to have a Catch of the Day with vigilance, ward {3}, and two “Whenever this creature attacks” abilities. You can even make the exact same ability choices as the original Catch of the Day, and the copy will have two instances of the chosen abilities. For instance, you can have a creature with ward {3} and ward {3} and “Whenever this creature attacks, scry 2” and “Whenever this creature attacks, scry 2.” Each of those abilities would trigger separately.

Catch of the Day doesn’t have any of the listed keywords, triggered abilities, or power and toughness combinations if it’s not on the battlefield.

Playtest cards aren’t legal for play in any tournament format other than Mystery Booster Limited formats. On the other hand, we expect they will spice up a wide variety of non-tournament games (as long as everyone’s on the same page about using them!).

Playtest cards use a modified version of game symbols, such as {T} and {W}. These modified symbols should be treated as the standard symbols during play.

For many playtest cards, you’ll need to make a generous assumption that basic game rules would be updated to allow them to work. The Mystery Booster 2 Playtest Card Notes section (reproduced here in individual Gatherer rulings) provides guidance for fitting these cards into the existing rules structure.