If I have a 0/0 with 13 +1/+1 counters on it and I or my opponent copies that creature, would it copy the 0/0 and die from its base power and toughness, would it be a 0/0 with 13 +1/+1 counters, or would it be a base 13/13 from copies the original creature's current power and toughness?
Copy effects copy the printed values —not the current values— of the object being copied, so the copy will be a 0/0.
706.2. When copying an object, the copy acquires the copiable values of the original object’s characteristics and, for an object on the stack, choices made when casting or activating it (mode, targets, the value of X, whether it was kicked, how it will affect multiple targets, and so on). The “copiable values” are the values derived from the text printed on the object (that text being name, mana cost, color indicator, card type, subtype, supertype, rules text, power, toughness, and/or loyalty), as modified by other copy effects, by its face-down status, and by “as . . . enters the battlefield” and “as . . . is turned face up” abilities that set power and toughness (and may also set additional characteristics). Other effects (including type-changing and text-changing effects), status, and counters are not copied.
If an existing object is becoming a copy (e.g. Lazav, Dimir Mastermind), pre-existing counters of its own or some pre-existing unmentioned effect (such as the one created by Arcane Flight's ability) would be needed to keep the copy alive.
- If copying a token, the token's initial values are copied.
It depends on both what is doing the copying and what exactly is the copied creature.
I'm going to assume the target creature is a Spike Feeder that you gave an additional 11 +1/+1 counters to. Those 11 +1/+1 counters are irrelevant because the copy will not have them.
There's basically two main ways to copy a creature:
- A Clone effect, that is something entering the Battlefield as a copy of the target. The game treats this copy just like how an original would enter. In our case, you would have a Spike Feeder that enters with 2 +1/+1s on it.
- Your opponent has an existing creature, e.g. Lazav, Dimir Mastermind, that can copy your creature. In that case, it will copy all it can which including the printed power and toughness but will not trigger any Enter the Battlefield abilities. So if your Spike Feeder died and Lazav chose to become a copy of it, he'd become a 0/0 and die due to state-based actions.
Final note, if you copy a 0/0 creature that enters with X +1/+1 counters (e.g. Apocalypse Hydra) with a Clone-like effect, the X used for the EtB effect will be 0 and the clone will most likely die immediately.