Copycrook

If the chosen creature is copying something else (for example, if the chosen creature is a Clone), then your Copycrook enters the battlefield as whatever the chosen creature copied, with the listed exception.

If no card is discarded, most likely because that player's hand is empty and an effect says they can't draw cards, the conniving creature does not receive a +1/+1 counter.

If a resolving spell or ability instructs a specific creature to connive but that creature has left the battlefield, the creature still connives. If you discard a nonland card this way, you won't put a +1/+1 counter on anything. Abilities that trigger "when [that creature] connives" will trigger.

If the chosen creature has {X} in its mana cost, X is 0.

Once an ability that causes a creature to connive begins to resolve, no player may take any other actions until it's done. Notably, opponents can't try to remove the conniving creature after you discard a nonland card but before it receives a counter.

If the chosen permanent is a token, Copycrook copies the original characteristics of that token as stated by the effect that put the token onto the battlefield, with the listed exception. Copycrook does not become a token.