In the beginnig there were Walter Hill, David Giler and Gordon Carroll; trying to make Alien^3. And they had William Gibson create a script. This script is mainly set around the East-West conflict as it could be in the future. Gibson's draft is rejected.
And out of all this emerged Alien^3.
Eric Red (The Hitcher & Near Dark) is then hired along with director Renny Harlin (Die Hard 2). Red's script, set in a colony of red-neck farmers (without Ripley) is rejected. Harlin hates the script so much that he quits.
David Tworthy writes two versions of a story set on a prison planet, one with Ripley and one without her.
Vincent Ward (The Navigator), hired as director, wants to set the story on a monastry on a wooden planetoid. Fox hires John Fasano to write Ward's version, telling Tworthy (who is busy rewriting at that moment) that Fasano's script is for Alien 4.
Greg Pruss is hired to rewrite Fasano's script. Pruss finds working with Ward hard going and quits over "creative differences". Fasano returns to rewrite his own script .
The Fasano/Ward partnership goes "out of control". Exit Ward as director. (The sets are already being built in London at that moment)
Enter 27-year-old commercial and misic video director David Fincher and Larry Ferguson (The Hunt For Red October) to rewrite Fasano's 'monks' script. Weaver is impressed with Fincher but not with Ferguson who, she said, had made Ripley sound like "a very pissed of gym instructor". Exit Ferguson.
Hill and Giler decide to write as well as produce. Their "emergency rewrite" reintroduces elements of Tworthy's prison planet script but retains the religious element of the Ward/Fasano period.
Rex Pickett is hired to rewrite the second half of the Hill/Gilger script. Pickett attacks both in a private memo supporting Fincher's input over the writer-producer's. Exit Pickett. Fox and Weaver are happy with the Hill/Gieler script, but Fincher has reservations.
Hill, Giler and Fincher fight for two months over the script. Fincher has problems with budgetary limitations.
Fincher is busy fliming the "perfectionist" Alien^3 in London. Against a backdrop of spiraling costs, Fox send "troubleshooters" to oversee Fincher. After seeing a rough cut, Fox pull plug and order Fincher with crew home.
Hill and Giler return to supervise post-production. An extensive list of reshots is drawn, but budgetary limitations and Weaver's refusal to shave her head again prevent the ending from being dramatically altered, despite obvious (but coincidental) similarities to the ending of Terminator 2.
And now it's all clear to you, isn't it? :-)