"Whimsy overflow in sector G! The gremlins are rampaging and the beetles are on fire!"

Alpha Guard

When this creature enters, choose a letter.
{T}: Untap another target permanent whose name starts with the chosen letter.

"Whimsy overflow in sector G! The gremlins are rampaging and the beebles are on fire!"

Unfinity

Because Alpha Guard appears only in Un- games, you may run into situations where cards that would normally have the same name—for example, an English-language Forest and a German-language Forest—now have different names. In Un- games, the name printed on the card is that card’s name (unless modified by stickers or other effects). Thus, if you were to choose F for Alpha Guard, you would be able to untap a Forest, but you would not be able to untap a Wald, Forest’s German equivalent.

When determining what a name starts with, ignore all spaces and punctuation, including blank lines.