Spotted Moon Snail
Guardian: Stephanie Blyth
All you have to do is replace the clam with a family sitting at home watching TV and you have an awesome Science Fiction Horror Movie Scene. A church size Spotted Moon Snail erupts from the back garden with a huge muscular foot reaching out and surrounding the house. The family have time to lock the doors and windows but a slimy mucous seeps in and slowly fills the rooms. Trying to hold it back, the father gets the slime on his hands and it paralyses him and then these spinning teeth emerge from the Moon Snail and drill through the wall and a proboscis (much like an elephant trunk) comes through the hole and devours everyone.
A few days later the police arrive to find an empty house with a perfectly symmetrical hole in the wall.