Star Trek: The Next Generation fans will likely remember the episode "Second Chances" in which it is revealed that Commander Riker has a genetic clone produced by a transporter accident earlier in his career. Then-Lieutenant Riker was assigned to the USS Potemkin, tasked with the mission of exploring an alien planet. Riker beamed down to investigate, but while he was transporting back up, a second annular confinement beam was initiated to adjust for the planet's unique atmospheric disturbances. That second beam allowed Riker to transport back to the Potemkin, but it also created a second, identical Riker, who was returned to the surface. Riker on the Potemkin, unaware of his doppleganger, went along his merry way... until some years later when the Enterprise (along with now-Commander Riker) returned and discovered his castaway twin.