Plot hole: If the groom didn't know who Lois was but had a picture of her, how could he have known that she was at the wedding so he could place the bomb in the blue sedan? If he had put the bomb in their car while they were still at home, they both would have been blown up. So this means he placed the bomb in the car at the wedding. He didn't know however that Lois was there until the end, where he caught up with them and told them not to start the car. Had he known earlier, he wouldn't have been arguing with his bride about the hit occurring during their honeymoon. (00:20:05 - 00:21:35)
Audio problem: After Lois goes insane and jumps out the window, she insults Frosty the Snowman, who then goes up to her to demand an apology. Lois then takes out a match and uses Frosty's nose to light it. Frosty recoils, holding his nose and saying "Ow, ow, what the-" but it cuts to a shot of Lois grabbing a bottle of beer from a hobo as Frosty is saying "What the" and it shows him standing perfectly straight, with his mouth not moving at all.
Continuity mistake: When Brian is giving his speech at the end, it shows two policemen. The one on the left has a brown drink and the one on the right has a yellow drink. But in the next shot, the one on the right has a yellow drink and the one on the left has a clear drink. (00:21:05)
Continuity mistake: When Peter is convincing Joe to do something with his life, they are listening to the news and beer cans are everywhere. Then the news reporter says, "Better watch out for that skateboard." After he slips, look around the room: there are no beer cans anymore.