 Although several androids, robots, and artificial intelligences were seen in the original Star Trek series (What Are Little Girls Made Of? and I, Mudd), Data was often referred to as being unique in the galaxy as being the only sentient androidknown to exist in the episode, " The Most Toys  " (save the other androids created by Soong).See the Star Trek: The Next Generation novel Immortal Coil, which explains what happened to all of these in the timeframe between the original series Star Trek and The Next Generation and how they relate to Data and Dr. Soong's other androids.
<meaning-changed>  Although several androids, robots, and artificial intelligences were seen in the original Star Trek series (What Are Little Girls Made Of? and I, Mudd), Data was often referred to as being unique in the galaxy as being the only sentient androidknown to exist in the episode, " The Most Toys  " (save the other androids created by Soong).See the Star Trek: The Next Generation novel Immortal Coil, which explains what happened to all of these in the timeframe between the original series Star Trek and The Next Generation and how they relate to Data and Dr. Soong's other androids.
 Although several androids, robots, and artificial intelligences were seen in the original Star Trek series (What Are Little Girls Made Of? and I, Mudd), Data was often referred to as being unique in the galaxy as being the only sentient androidknown to exist in the episode, " The Most Toys " All Good Things...", the two-hour series finale of The Next Generation novel Immortal Coil, which explains what happened to all of these in the timeframe between the original series Star Trek and The Next Generation and how they relate to Data and Dr. Soong's other androids.