If the copied creature has in its mana cost, X is 0.

If you are instructed to put a card that isn't a double-faced card onto the battlefield transformed, it will not enter at all.

In some rare cases, this permanent might transform while its triggered ability that allows you to pay mana to transform it is still on the stack. (For example, another effect might cause that ability to trigger an additional time.) In such a case, even if you pay mana as the triggered ability resolves, this permanent won't transform because it already transformed while the triggered ability was on the stack.

If the copied creature is a token, the token that's created copies the original characteristics of that token as stated by the effect that created that token, with the listed exception.

Each face of a nonmodal double-faced card has its own set of characteristics: name, types, subtypes, abilities, and so on. While a double-faced permanent is on the battlefield, consider only the characteristics of the face that's currently up. The other set of characteristics is ignored.

In the Commander variant, a double-faced card's color identity is determined by the mana costs and mana symbols in the rules text of both faces combined. If either face has a color indicator or basic land type, those are also considered. For example, Oko, Lorwyn Liege's color identity is green and blue, since its front face is blue, its rules text contains a green mana symbol, and its back face has a green color indicator as well as a blue mana symbol in its rules text.

The mana value of a nonmodal double-faced card is the mana value of its front face, no matter which face is up.

The token created by Grub, Notorious Auntie's second ability copies exactly what was printed on the original creature and nothing else, with the listed exception (unless that creature is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.

Any enters abilities of the copied creature will trigger when the token enters. Any "as [this creature] enters" or "[this creature] enters with" abilities of the copied creature will also work.

Each nonmodal double-faced card in this release is cast face up. In every zone other than the battlefield, consider only the characteristics of its front face. If it is on the battlefield, consider only the characteristics of the face that's up; the other face's characteristics are ignored.

If the copied creature is copying something else, then the token enters as whatever that creature copied, with the listed exception.

A token that is created as a copy of a double-faced permanent or a double-faced card in another zone is a double-faced token. It will have both the front face and back face of whatever object it's copying. If it's copying a double-faced permanent whose back face is up, the token will enter with its back face up. It can transform if instructed to do so.

The back face of a nonmodal double-faced card usually has a color indicator that defines its color.

If a creature's toughness is reduced to 0 while blighting during the resolution of Grub, Notorious Auntie's second ability, that creature won't die until after the ability finishes resolving. The same is true if the -1/-1 counter would cause damage already marked on that creature to become lethal.

A nonmodal double-faced card enters with its front face up by default, unless a spell or ability instructs you to put it onto the battlefield transformed or allows you to cast it transformed, in which case it enters with its back face up.