Sandworms are alien monsters from saturn and the minor antagonists from the film Beetlejuice.
When Adam and Barbara died, they went back into the house and Adam check to walk back out the door, but then the outside begin to change into a dark sandy night. Adam heard a strange roaring noise and saw a coiles sticking out of sand but Barbara grabs Adam back into the door.
Barbara walks out of the door outside and fells down to the saturn, she was lost and Adam went out to saturn to look for her, when they found each other, the growling noise appears from far away crawling in the sand and the sandworm pops out to eat them, but Barbara hits the sandworm and it shakes it's head and then it's about to eat them again, but Adam and Barbara went back into the door.
In the second appearance. Betelgeuse sends Barbara back into the sandworm land, she rides the sandworm back into the house and it eats Betelgeuse up Barbara jumps off and the sandworm crashes through the floor.