Wiktionary
space alien
n. (context chiefly US English) An extraterrestrial being; a visitor from outer space.
Usage examples of "space alien".
Stories featuring women who claimed to have given birth to space alien babies were popular fare at the supermarket checkout counters.
Crap like that was three steps below CHER ADMITS BEING SPACE ALIEN, two steps below JESUS SPEAKS TO NUN FROM INSIDE A MICROWAVE, and even a full step below ELVIS HAD BRAIN TRANSPLANTED, LIVES NOW AS ROSEANNE BARR.
Believe me, I would much rather have blamed my abuse on a space alien than have to face the truth about what happened to me with the adults I was supposed to be able to trust.