Revealing mistake: When Frank ties the bedsheets together to the sink, he ends up pulling the basin off the pedestal. Surely that would cause a flood, but we don't see any water come out at all.
Continuity mistake: When the wardrobe falls onto its side you can see that Frank hasn't broken the base. However, when he hides in it out on the landing, he is able to walk about inside it, moving the wardrobe with him.
Continuity mistake: When the other guest goes out into reception and asks "Mr. Bedford, all quiet?" in one shot he is wearing his dressing gown, but the next he's just wearing pajamas.
Continuity mistake: When Frank and Betty place their wardrobe down, it nearly goes through the floor because the boards are damp. First Frank tries putting wood under it (from the drawers), then after breaking the wardrobe door he swaps the wardrobe with another guest's. They place that wardrobe in the place where the damp boards were without putting any wood underneath, and don't seem to have any problems with the damp floor.
Revealing mistake: When Frank and Betty move the wardrobe, the walls wobble.
Other mistake: As Frank and Betty move the wardrobe a chair tips over by itself. Frank and Betty are nowhere near it - it is presumably attached to a wire which is pulled by one of the crew, but has no significance to the plot.
Revealing mistake: Before Frank pulls the mat from under the wardrobe and tears it, you can see the mat is already torn and placed back together.
Audio problem: After Frank has torn the lino by moving a bed, he tries to neaten it up only to tear it more. The sound effect is not in line with the tearing of the lino.
Continuity mistake: During the roller skate sequence he is wearing a jumper, then before he enters the shop he is in only a shirt, then back to a jumper inside the shop.
Revealing mistake: When Betty goes into labour in the night and goes downstairs with her suitcase, she tries opening the front door. You can see it moving with her pulling. And then when Frank goes to climb out of the window to follow the key, he climbs onto the sink, which almost rolls away, which reveals the fakery of the set.
Jessica's First Christmas - S2-E7
Visible crew/equipment: When Frank is loading the lorry at the warehouse, he drives the forklift onto the lorry, then the lorry drives off while he and the forklift truck are still on the back. As the lorry pulls away you can see the camera crew on the other side of the road filming the next shot.
Jessica's First Christmas - S2-E7
Other mistake: When Frank open his front door to Mr. Jackson the walls around wobble.
Jessica's First Christmas - S2-E7
Revealing mistake: When the second piece of scenery falls on Frank, it has a tear halfway down and a hole in it that Frank's head goes through. A few seconds earlier, these weren't there. Maybe they were put there to make sure Frank's head went through, or else this is the second take.
Jessica's First Christmas - S2-E7
Deliberate mistake: Just before father O'Hara explains to Frank why he isn't in the nativity play he says to Betty "Perhaps I will have that cup of tea after all Mrs. Spencer" Betty goes to the kitchen but father O'Hara never gets his cup of tea.
Suggested correction: Perhaps Betty just forgot.
Jessica's First Christmas - S2-E7
Revealing mistake: At the final rehearsal for the church nativity play when Betty first comes on stage with baby Jessica wrapped up in a blanket and places her in the manger, it is obvious that Jessica is actually a doll.
Jessica's First Christmas - S2-E7
Continuity mistake: When Frank is demonstrating his star trap to Father O'Hara, Frank comes up through the stage floor too fast and grabs hold off a length of material stretched across the top of the stage which falls down onto the stage floor when Frank falls, but in the following shots of the scenery collapsing this piece of material has disappeared.
Jessica's First Christmas - S2-E7
Revealing mistake: The walls of Frank and Betty's bedroom wobble when the door is shut.
Jessica's First Christmas - S2-E7
Visible crew/equipment: When Frank asks Jackson if he can work the crane, there is a boom mike shadow on the wall to their left.
Revealing mistake: When Frank is the pixie in Santa's grotto, a young boy fires something at Frank from his catapult. Although Frank reacts as being hit, the boy doesn't actually fire anything at all.
Other mistake: The walls of Frank's house wobble whenever he opens the front door.