The abduction of someone against their will by space aliens.

Examples:
Captain Picard was abducted from the Enterprise-D by a pair of unnamed aliens and replaced with a replica in tng3x18 "Allegiance". Aliens abducted Fry and took his nose in futurama4x17 "Spanish Fry". In the widely lampooned film "Santa Clause Conquers the Martians" (1964), mean-spirited Martians abducted Santa Clause at ray-gun point and hightailed it home, not knowing that the jolly old man would bring the spirit of Christmas to the Red Planet. Thus featuring the crackpot theory theme "alien abduction".

References:
https://en.wikipedia.org/wiki/Alien_abduction