Does a copy of a spell on the stack inherit the targets of the original?

When a spell or ability creates a copy of a spell on the stack, the copy starts out with the same characteristics as the original — same name, mana cost, effects, and so on — but it does not automatically inherit the original's targets. Instead, the player who controls the copy must choose new targets for it at the time the copy is created (CR 707.10).

This is a crucial distinction: the copy is placed on the stack and then, as part of that same process, the controller may (and must, if the spell requires targets) select fresh targets. Those new targets can be the same as the original's or completely different — it is the controller's choice (CR 707.10).

If the copy has multiple targets, each one must be chosen anew. Targets that were illegal for the original may still be chosen for the copy, and vice versa — legality is checked independently for each object on the stack (CR 608.2b).

Concrete example: Your opponent casts Lightning Bolt targeting your creature. You cast Twincast to copy it. When the copy of Lightning Bolt is put on the stack, you choose a new target for it — say, your opponent's face (they become the target). The original still targets your creature. Both spells resolve independently with their own targets.

This rule prevents copying effects from being trivially negated by making the original's target illegal after the copy is already locked in; each copy stands alone with its own chosen targets evaluated at resolution (CR 608.2b).