Despite all the excitement over the potential third Ghostbusters or new Alien movies, there's one element of both that'll be missing even if both end up happening: Sigourney Weaver has said that she won't be appearing in either.
Talking to Sci-Fi Squad, Weaver said that the chances of her appearing in a new Ghostbusters movie are "[p]robably non-existent... I don't expect to have anything to do with it, although I wish them well." She's similarly downbeat about the potential for an appearance in the much-discussed Alien prequel, for practical reasons:
Well, I don't think that Ripley could appear in an Alien prequel because she doesn't have any access to the creature until the first Alien. But Ridley (Scott) is producing it and that makes me happy. I wasn't thrilled with the whole Alien Vs. Predator thing. I never saw them, but one of the reasons I died in (Alien) 3 was to not have anything to do with those (laughs). Just because, you know, I think it just seemed so economically motivated somehow. I feel we did four good movies, and I'm content with that. I hope if they do something new, they will encompass the idea of where the alien first came from, because I think that's an interesting idea — to find out what happened and "how did it get to us?".
There goes my spec script where Ripley's clone time-travels to the past to place the Alien eggs on that planet in the first place, then...
Sigourney Weaver Talks About 'Ghostbusters 3,' 'Alien' Prequel [Sci-Fi Squad]