Factual error: The sheriff does not come to your house and take your credit cards just because they are maxed out. The only time they would do that is if you stole someone else's card and were using it.
Sixteen Years and What Do You Get - S1-E6
Plot hole: Peg maxes out the credit card buying Al anniversary gifts and hiring a caterer. When Al tries to buy a watch for Peg it's declined. Later on Kelly somehow uses the credit card and is able to buy the expensive picture frame at the same store Al tried to buy the watch.
Continuity mistake: After Bud's Hail Baby, the spoon that had been to the right of Peggy's glass, changes position.
Continuity mistake: When Al and Peg are on the couch, the ice bag changes position.
Visible crew/equipment: When Bud and Kelly are sitting on couch, after Al goes upstairs, you can see the shadow of crew/equipment go across Bud's shirt from right to left.
Build a Better Mousetrap - S2-E15
Revealing mistake: Al smashes his finger while holding a piece of cheese next to the hole in the wall. But you can see the hammer wasn't near his finger at all. It hits the wall.
Revealing mistake: Obvious dummies when Al tosses Peg off him on one of their separate beds and when Al falls through the bedroom floor to the den.
Other mistake: When Sonya takes off Bud's bandages on his arms you can see they aren't injured.
Kelly Doesn't Live Here Anymore - S7-E8
Revealing mistake: You can plainly tell that Kelly is wearing a beehive wig at the diner when Peg comes and talks to her.
You Better Shop Around (2) - S5-E22
Revealing mistake: Watch Jefferson and Marcy's feet at the end. They start to trip before the turkey even hits their feet.
Plot hole: In this episode Al is about to break Puggy Weaver's record. Peg decides to bowl and scores a perfect score of 300. Problem is Peg is a horrible bowler, as seen in season 2 episode 9. She never bowls with Al or even enjoys bowling, so this episode really makes no sense.
Suggested correction: This is not a plot hole, but a plot point. Yes, Peg is a horrible bowler, but it's typical Al Bundy luck that his wife would be able to put together a perfect game no matter how unlikely.
So this one and only episode she scores a perfect game? Highly unlikely. Oh and she's wearing a long evening dress too which would make it difficult to bowl. So this episode makes no sense.
It makes perfect sense. In the world of the show, the universe is out to screw Al over. The worst that can possibly happen to him will happen no matter how unlikely.
It is a comedy, so having all those "strikes" against her, she still managed to bowl a perfect game - leaving Al hopeless and hapless.
Master the Possibilities - S2-E16
Factual error: Buck may have got a credit card in the mail but Al would've got jail time for credit card fraud considering he signed Buck Bundy on all the receipts.
Dead Men Don't Do Aerobics - S4-E2
Revealing mistake: When we see Jim Jupiter on his show after gaining weight, you can plainly tell he's wearing padding under his clothes to make him look fat.
So This is How Sinatra Felt - S6-E12
Plot hole: Bud and Kelly hide behind the cash register all day. They talk normally the whole time yet Al doesn't hear a word they say and has no idea they are even there.
Factual error: Al plants a vegetable garden. 6 weeks later his garden is shown with fully developed vegetables including full stalks of corn. Not possible in a month and a half.
Other mistake: The Bundys never lock their front door the entire series, but a burglar has to use a crow bar to open the sliding glass door out back.
Revealing mistake: The burglar uses a crow bar to open the sliding glass door. You can plainly see him "pretending" he had to use it when it just opens easily. He didn't really pry it open.
I Can't Believe It's Butter - S10-E13
Plot hole: Griff doesn't know Peg's mom is Butter. He comes to Al's wanting to meet her. Al gathers the family to talk about what to do. They say Griff can't know its Peg's mom, yet they talk out loud and Griff is standing right there while they are sitting at the kitchen table. It's not until the end of the episode he finds out.
Movie Show - S7-E21
Revealing mistake: When Kelly is eating the boxes of candy you can plainly see they are empty, but she's chewing anyway.
Revealing mistake: Kelly lost all her hair as a side effect from pimple potion. You can see the lines on her forehead that show she's wearing a flesh piece covering her hair to make her look bald. The color is lighter than her face. (00:18:42)
