Starkiller
Super Freak
There was no CGI in A3.
It was all done with a rod puppet (the last cool thing ADI did for the Alien franchise -wait, let me correct that- the only cool thing ADI did for the franchise) which was inserted into the movie. Those were all old-school optical effects.
The alien is played by Alien Effects Designer Tom Woodruff, Jr. wearing a costume designed by himself and Alec Gillis, and also appears in the form of a rod puppet filmed against bluescreen and optically composited into the live-action footage. A mechanical alien head was also used for close-ups.
A small number of shots contain CGI elements, most notably the cracking alien head. Other CGI elements include shadows cast by the (rod puppet) alien, and airborne debris in outdoor scenes.
The bluescreen scenes where you can tell in all of them that that alien was placed there and the cgi looked very fake and crude then.