Watch the episode where Al takes his mom out to dinner to tell her that he is going to propose to Trudy. Tim and Jill are at the restaurant that night also. Start watching closely when Tim says something like, "Ok, I think he's going to tell her now, he took the ring out." Al takes the ring out and tells his mom that he is going to propose to Trudy. His mom faints and falls on the floor. Right after she falls, nothing happens. But a COUPLE OF SECONDS later, the set is purposely shaken to give the effect that Al's mom shook the ground when she fell. It would definitely not take that long for the ground to shake.