Director Ridley Scott has said that his original planned ending for 1979's "Alien" was not for Ripley to succeed in killing the alien and going into suspension, but for the alien to actually rip her head off. This reportedly infuriated studio execs to such an extent that they threatened to remove him from the project if he proceeded in that direction. So Ripley (and her cat) got to survive to fight the xenomorphs another day. Probably a wise decision for the sake of sequels at least.