Doppelganger is a Continuous Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Doppelganger is Unlimited.
YGOPRODeck lists Doppelganger for these formats: Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Doppelganger appears in Crossroads of Chaos (CSOC-EN070) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Doppelganger is about $0.06 on Cardmarket (prices change frequently).
