Other mistake: In the beginning of the film when you're introduced to the younger, humanoid Sil in the laboratory, an extreme close-up of her eyes and face clearly reveals the young actor's contact lenses.
Other mistake: When Sil jumps through the hotel room wall, Pres fires two shots from his Glock and then gets in the elevator. In the elevator he drops the magazine and his Glock has the slide locked back showing the magazine is empty. The man is an acknowledged expert in special ops (Indeed, the fact that he changes magazines in the elevator demonstrates his preparedness. He wants to face Sil with every bullet he can, he doesn't want to be even two short.) He is going up against an extremely dangerous extraterrestrial life form that has already killed several people. There is absolutely no way he would be carrying a weapon that was not fully loaded.
Other mistake: At the end, during the final showdown, Laura falls into the oil and it is deep enough for her to need to swim in it, but she is completely clean afterwards. Even her jeans are spotless in the next scene when they reenter the sewers and the camera is zoomed out, showing her legs.
Other mistake: It's impossible for Sil to wear the conductor's clothes. She's tall and slim around maybe 5'9" while the conductor looks to be 5'5"or so and a little chubby.
Suggested correction: It's not "impossible" in the slightest. Both women were roughly the same height. Natasha Henstridge is about 5'10" and Esther Williams was usually listed around 5'9" or 5'10" before she passed away. And the weight difference also makes sense, as the clothes look baggy and ill-fitting on Sil. (Ex. The jacket is very loose and hanging around her shoulders and arms, and the shirt isn't nearly as form-fitting as it was on the conductor.) It's pretty much perfectly portrayed in the film.
