Revealing mistake: When Kelly enjoys her triumph at the middle of the stairs you can see a shadow on the wall right from her - obviously Al stands behind the wall waiting for his cue. (00:19:00)
Can't Dance, Don't Ask Me (aka Kelly's Dance) - S3-E13
Continuity mistake: While Kelly is dancing with the guy at school, a nerd girl starts kissing on Bud and pushes him backwards. The very next second when the scene changes, Bud on the left side is back playing the record for the music without anyone around him.
And Bingo was Her Game-O - S9-E21
Factual error: The "Geo Metro" in which Peg and Marcy ride looks nothing like a Geo Metro.
Other mistake: Peg reads from a headline saying "[Marcy] announces NBC fall schedule, people still disappointed." But the text below it reads "State officials..." showing the text doesn't belong with that headline. Also when you see each headline the article is the same for each one.
You Better Shop Around (2) - S5-E22
Plot hole: The supermarket director orders the photographer to take a photo of Al's special shopping cart. Then he turns around a little towards the cart. When the camera flashes, his right shoulder has to be in the whole left side of that picture. (00:07:50)
You Better Shop Around (2) - S5-E22
Revealing mistake: When Al 'bowls' Jefferson out of the way you can see the stuntman jump high and fall back into some kind of holding wire. It's an annoyingly bad stunt. (00:19:45)
You Better Shop Around (2) - S5-E22
Continuity mistake: The manager gives Jefferson a "wobbly" cart to use, but for the rest of the episode it's a normal, fast moving cart.
Guess Who's Coming to Breakfast, Lunch and Dinner - S10-E1
Revealing mistake: Near the beginning when Al is looking for his magazines under Bud's bed, a large shadow of someone crosses over him showing someone in production crossed in front of the lighting.
Desperately Seeking Miss October - S4-E7
Revealing mistake: In the scene where Al and his Dad (both played by Ed O'Neill) are sitting on the couch side by side watch the lines of the cushion in the middle. Every time one of them moves you can see where the two separate shots are overlaid. (00:14:15)
Breaking up is Easy to Do (2) - S11-E15
Continuity mistake: Before the dinner date, Peggy takes a plate of raw meat out of the dishwasher. Bud and Kelly go to help her put it on the stove, but Peggy's plate is now empty and the meat is on another plate already on the stove. Yet strangely, Bud and Kelly take the empty plate from her anyway and put it on the stove next to the other one.
Visible crew/equipment: At the beginning of the Last Will reading we see that there's no-one sitting left to the female notary. But in the close-ups there is a small round silver-shining object at the right edge of the picture - left from her. Must be some equipment. (00:04:20)
Visible crew/equipment: When Peggy enters you can see the shadow of someone's head at the left edge (the kitchen). It can't be anyone of the actors. (00:12:05)
Continuity mistake: When Al Bundy drops the stiletto shoe into the fish tank, he reaches down into the tank to get it and his sleeve and hand are dry as he shows the shoe. Also, hardly any water drips off the shoe. (00:17:00)
Continuity mistake: In one of the scenes where Bud is forcing Kelly to eat, he tries to feed her cheese whiz but she resists and some of it gets on the side of her mouth. In the very next shot, when Peg runs in, the cheese is no longer on the side of Kelly's mouth.
The House That Peg Lost - S3-E16
Plot hole: Marcy and Steve live on the left-hand side of Al and Peg yet when they come home and see their house is gone Peg is looking out the window in the front door saying they're looking at the hole now they're looking over here.
Other mistake: When at the gas station, they are out of gas. He doesn't put any gas in but later Peggy starts the car up and drives away.
Poppy's By the Tree (1) - S2-E1
Revealing mistake: When Al, Peg, and the kids get to their room, notice the "hole" in the blanket on the bed. It's there the entire episode so at the end, the killer can shove the machete up through it.
Continuity mistake: Al takes the kids camping. When he leaves the house, his shirt is light blue. When he comes out from the bushes in the woods, it's dark blue with red stripes.
Revealing mistake: At the start of the episode, Peg is making popcorn on the stove. It's making a sizzling sound like she's really popping it but the burner isn't even on.
Other mistake: Al's and Peggy's birthdates are around 1948/1950, respectively. Supposedly, Al married Peggy after she got pregnant the day of his 4 touchdowns in high school in 1966. How could Kelly have been born in 1971?
Answer: Bud's date is a foreign exchange student and Kelly was wondering what was sent to the country Monique was from in exchange for Monique being sent to America.