A Farewell to Writing - S4-E33
Revealing mistake: Laura and Millie are inside the "house" and Rob is outside the "house" the door and windows are all closed... Yet we can still hear Rob just as if he was in the house rather than outside.
A Farewell to Writing - S4-E33
Character mistake: Rob was digging outside the window supposedly with his hands. Yet he is 100% clean as a whistle. No dirt on anywhere to be seen.
A Farewell to Writing - S4-E33
Other mistake: Rob said he hit the plumbing (with a shovel) yet if you hit the plumbing (accidentally poke into a plumbing tube) usually water would shoot all over the place (which never happens in this episode).