Spock One

From Memory Alpha, the free Star Trek reference

Spock One was a hologram created by the Romulan Sela. She obtained his image for use in the program during meetings between the real Spock and Proconsul Neral. The program was not interactive, and was unable to respond to questions.

She created it to be used in the event of Spock refusing to read a statement encouraging the Vulcans to welcome a peace envoy from Romulus. The peace envoy was a plot to send the Vulcan ships, full of Romulan troops, to conquer Vulcan. It was not used, however, due to the intervention of Spock, Data, and Jean-Luc Picard. (TNG: "Unification II")