The house that belonged to Dr. Giggles was not a real house but a prop that was set up in a park. The crew built this prop house instead of using a real home so they could blow it up toward the end of the film.
When Dr. Giggles' house blows up, Jennifer and her boyfriend fall to the ground twice.
SPOILER: When Jennifer is wheeled into the operating room, the nurse finds blood on the floor and discovers two bodies. Later, after the doctor has killed Jennifer's surgeon, she runs out of the same door, but there's no blood.