Any extraterrestrial, most likely with some level of insanity and/or psychotic tendencies, that poses as the sister of any legitimate human. May emit, at any volume, the following: doggy voice
, shrill sounds, nonsensical words, sudden shouts, low hissing sounds, extremely bad whistling, or other bizarre noises.
"Why is my little sister so annoying?" "She's probably an alien psycho sister."