I vaguely remember channel surfing in the late 90's and seeing a horror movie scene in which a woman emerges from a portal/gate/wormhole and says something like "there's thousands of them!".
She is suddenly impaled from behind, and an alien's insectoid head appears over her shoulder. She is then dragged back into the portal.
I was called away from the TV at that point, but the scene has stuck in my mind as an example of a pre-CGI monster/alien, and I remember thinking that the creature effects looked too expensive for a TV show.