Producer Frank Mancuso Jr. wanted the creatures to look slightly different from H.R. Giger's original concept. He did not contribute to the designs in this film and the creatures were redesigned by Rob Hinderstein.
A scene which was changed due to budgetary reasons had Sara scratch a campus student's cheek with her alien finger, which looked like a spike. Instead, this was changed to Sara throwing the man over her into a hedge in the final film.
In the first film, Dr Laura Baker likened humanity to a galactic weed spreading throughout the galaxy like The Day of the Triffids on Earth, Invasion of the Body Snatchers, or Quatermass which had tripodal Martians.