According to the comprehensive rules: if there are fewer than N cards in your library, you may reveal all the cards in your library. If you cast a card with ripple 4, and there are only 3 cards in your library, you will just reveal all three of those cards
You see that Feraligatr coming at you, and you run
That is also the reason it is not possible to say where the sheet starts and where it ends
This ability also lends itself very well to combos, unlocking infinite enters/dies lines with cards like Tortured Existence and Phyrexian Altar, for example
Acorn cards are indicated by the new Unfinity acorn security stamp at the bottom of MTG cards
The panic appears to have been relatively short-lived, and Van Gogh Pikachu is rapidly retaking the ground it lost