The Krusty doll changes sizes throughout the first segment. He's just a little shorter than Maggie at times, but later he's as small as a Barbie doll and can fit in the doll house.
The shopkeeper takes the doll down from the shelf without a box. Yet the doll is in a factory-standard box when it's given to Bart. (Clearly, Homer was able to wrap the box before giving it to Bart, but it should've been in a plain box if it was in one at all.) This is the box Marge uses to call the helpline at the end of the segment. However, it is possible the box came with the doll and the doll was simply put on display outside of it.
When Homer gets attacked by the Krusty doll and flies into the kitchen, the kitchen's table is missing.
The Krusty doll's teeth change from rounded to pointed to rounded again several times.
Homer takes Marge from at least a second-story window. He then climbs two more stories and places her on allege. However, when he falls Marge is sitting on a third story ledge.
In "Dial Z for Zombies," we see a picture of Snowball, the Simpsons' first cat, but in the picture, Snowball is black, just like Snowball II. Snowball was a white cat.
Homer runs off camera to buy Bart a birthday gift but part of Homer's white shirt can still be seen in frame.
Homer purchases a solo Krusty doll; however, when he returns home and gives Bart his present, the Krusty doll is contained in a box. Later on, Marge finds the customer service number for the Krusty doll on a box, despite the fact that Homer bought the doll at a curious shop owned by a strange Chinese man and it clearly wasn't in a box when he bought it from the start of it.
After Homer returns home from eradicating the evil Krusty doll and it attacks him; Homer screams visually even though he's talking. Likewise, none of his dialogue syncs up with his mouth - as it is agape and doesn't move.
When the Krusty doll calls Homer a "stupid idiot", his mouth doesn't move.
Marge tells Homer "Maybe you should eat more vegetables and less people." It should be fewer people.