Stunt Double

Clone with flash is a different animal than clone at sorcery speed, and that gap is what this design is built to exploit. The original Clone copies during your main phase, when the board is settled and everyone can see what you picked. Flash collapses that window: you hold up four mana, wait for an opponent to resolve their best threat, and then become it at the most punishing moment. That covers arriving as a copy of a creature with a relevant enters-the-battlefield ability, blanking an attack by suddenly matching the biggest blocker, or duplicating a freshly cast bomb the turn it lands so the advantage is split rather than one-sided. The copy is a replacement effect and optional, but declining it is a trap: the printed body is a 0/0, so if you choose not to copy anything, it enters, fails a state-based check, and dies immediately with nothing to show for it. The same fate awaits it when the board is empty of other creatures to copy, so in practice you cast it only into a target worth becoming. Shapeshifters had been copy creatures for a long time before this, but most paid for their flexibility by committing on your own turn. Pricing the copy at instant speed converts a reactive body into a trick, a counterspell-adjacent answer that leaves you ahead on the board rather than merely even on the stack.