A comet discovered by the Enterprise is found to be the archive of the ancient D’Arsay civilization. Soon parts of the starship are being converted to artifacts of this culture. The program also targets Data and makes him impersonate different iconic characters. Eventually, Picard and the others deduce that Masaka, the most feared character, and her pursuer, Korgano, share a cycle much like Earth’s sun and moon. With time running out and direct override impossible, Geordi finally locates the archive’s transformational program just in time for Picard to assume the “mask” of Korgano and “chase” Masaka off her temple throne. Once Masaka is subdued, both the ship and Data return to normal without the whole society of characters that were once within him. summary by Ex Astris Scientia
The only thing I found fascinating about this - otherwise completely stupid - episode was Brent Spiner’s performance. Those different personalities surfacing one after another, signalled by his whole body language, it’s a must-see, not only for Trekkies.