Revealing mistake: When the mall Santa lands in the Bundys' back yard, everybody looks toward the back, and when Al looks forward, he cracks a smile although he's upset about the matter. Ed O'Neil admitted he couldn't contain his laughter.
Build a Better Mousetrap - S2-E15
Continuity mistake: When Al hits his thumb with the hammer when trying to hit the mouse in the wall, he hits his left thumb. In the very next scene, Peggy is wrapping up his right thumb.
Poppy's By the Tree (2) - S2-E2
Revealing mistake: When Al is blocking the killer's axe with his suitcase and they struggle for it, it is obvious that the axe is made of rubber, as the handle keeps bending.
Poppy's By the Tree (1) - S2-E1
Factual error: At the end of the episode, the killer shoves a long machete up through the mattress. This isn't possible considering he's under a bed and there's not enough vertical space to shove a machete straight up.
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.
Plot hole: Al comes home from work. He purposely doesn't look in the kitchen, so he can act like he's surprised it isn't Peg that brings him a beer. Steve talks and Al acts surprised that he's there. When you walk in the front door you automatically see the kitchen.
Suggested correction: It's quite possible to do this. My house has a similar layout: front door opens into the living room, and the kitchen is at the back of the living room. I can come inside and walk to the couch without paying attention to the kitchen. Plus, Al is cranky after work - he says "Ah, what a day" - and he is focused on getting to the couch and relaxing.
This is the only episode where Al does this... Just because he knows it's Steve and not Peg. Pretty obvious.
Just because something is only shown in one episode, that doesn't mean it has never happened before. And because he said "What a day", it seems that his work day was especially frustrating, busy, etc. It's reasonable that he could focus on getting to the couch, not bothering to look at the kitchen.
Just Married ... With Children - S2-E20
Other mistake: Al gets sat on by 3 heavy women. The scale says 927 pounds. 4 more women sit down and the scale says 1071. So 4 more heavy women only added 144 pounds? Impossible.
Just Married ... With Children - S2-E20
Other mistake: Al and Peg win a new Mustang in this episode. It's never seen again.
Continuity mistake: Marcy tells Peg that Steve has been gone for 5 days. Yet when he gets home, he has grown a full beard. It would take longer than 5 days to grow a full beard like that.
Girls Just Want to Have Fun (1) - S2-E5
Continuity mistake: When we first see Peg and her friends at the kitchen table the fridge door is closed. Steve comes in with flowers and the door is open. He goes into the kitchen and it's closed.
Im-Po-Dent - S2-E19
Revealing mistake: Bud and Kelly put Tang in glasses. Al says "what are you hiding?" They quickly "drink" it but the glasses are empty.
Poppy's By the Tree (1) - S2-E1
Continuity mistake: Bud asks to go down to the high school "tomorrow" to meet the man who met Andy Griffith. Earlier Al reads the events page in newspaper. The event was said to be "tonight."
Girls Just Want to Have Fun (2) - S2-E6
Continuity mistake: When sitting on sofa with Marci, Peg's necklace falls beneath her red blouse. It remains under in most shots, but in the last shot it is outside her shirt.
Poppy's By the Tree (1) - S2-E1
Continuity mistake: When Kelly walks over to the table, she burps. She breaks character by laughing with her head down yet a second later, she has a serious look on her face.
Peggy Loves Al, Yeah Yeah, Yeah - S2-E17
Other mistake: When Bud goes upstairs with his fake bag of "Valentines" (actually a bag filled with bottles), Kelly begins to look through some from her bag. Behind her, you can see David Faustino (Bud) purposely moving slowly up the stairs because Christina Applegate (Kelly) is about to find the envelope that is addressed to Bud.
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.
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.
Girls Just Want to Have Fun (1) - S2-E5
Continuity mistake: Al is having his fridge repaired. He goes and gets a beer and closes the door. A few shots later the door is wide open without anyone going near it.
Factual error: It seems unlikely Steve's bank or any bank would leave its vault open at night as they close around five or six.
Suggested correction: Steve is the bank manager and is closing up for the day. There is also a security guard sitting right by the door. And he has to unlock the door to let Al in. No mistake here.
The mistake is about leaving the vault door wide open instead of closing it. Not about Steve needing to unlock the front door to let Al in.
My point is Steve is closing the bank with a security guard there and the door is locked. So what if the vault is open? Steve just hasn't closed it yet.
Poppy's By the Tree (2) - S2-E2
Plot hole: Al and Peg are upstairs with the killer. Both of them are screaming, but downstairs, you can't hear anything. Everyone is sitting around talking. It's not until Al and Peg scream again that everyone runs upstairs. And you can tell the screams were "on cue" also.