Visible crew/equipment: At the beginning episode 5.9, "Chicago Hope", the camera and several studio lights reflect on the glass door behind Tim as he sits at the dining room table.

Deliberate "mistake": When Jill turns off the light to Randy's room, she uses the same switch that Al used to activate the reverse laundry chute.

Revealing: Anytime the kids are shown running through the backyard, it sounds very obvious they are running on a wooden set floor instead of real grass-covered ground.

Revealing: When Wilson and Tim start to talk they sit down on some rocks. If you look at Wilson's foot you can see the sheet of fake snow caught under his foot.

Revealing: At the beginning during the Binford commercial, Tim falls off the ladder that they just set up and it's possible to see it's connected to the wall (so it will flip, but not fall over).