Other mistake: When Quagmire is sticking his body out of the car door and yelling "Whooooooa! Whoooooooa!", look at the person in the back seat. It certainly isn't Joe, who was there in the previous shot, in fact it looks like another Quagmire.
Other mistake: After the hurricane passes, Peter acts like he's been impaled by a wooden plank. He pulls it out as if it was attached to his right side. However, the way the metal on the clasp was bent, the only way the wooden plank could've been positioned that way is if the metal was over his shoulder.
Other mistake: Peter goes back in time and sees Lois at age 18. Death says everyone will see Peter as being 18 too. Problem: Lois and Peter aren't the same age. In later episodes, Lois reveals she's 2 years older than Peter so Peter should be 16 when he meets Lois.
Other mistake: Everything goes backwards in time and goes that far back that Meg (who is voiced by Mila Kunis) goes back to being voiced by Lacey Chabert (who voiced Meg in season 1). However, when Lacey Chabert does her line to Stewie being in the Griffin house for the first time, it goes back to Mila Kunis when Stewie is "reborn". However, if everything was going backwards and Brian fixed everything to make it goes forwards again, then it still should have been Lacey Chabert voicing Meg, not Mila Kunis.
Other mistake: When everyone is leaving the mansion after Stephanie was killed, 3 mistakes happen at the same time: Dr. Hartman came alone, but there is a person sitting in the front seat next to him. Derek is in the car he and Jillian came in when they got here, but he is alone. And Carl was getting into Herbert's Ice Cream Truck, which was in front of his own truck.
Other mistake: During the scene at the rehab clinic when Brian is jogging, Peter asks if he wants to go "mess with the pregnant teens across the lake." Brian says no because "Group therapy, two o'clock." However, the sky looks as if the sun is about to rise or just set. The time cannot be anywhere close to 2:00, neither AM nor PM.
Other mistake: As Joe is driving up to the house, just before coming to a complete stop, you can see that his window is completely closed. After stopping, Peter says "Joe?" Joe says "Peter?" Joe's window is now fully open. Trouble is, Joe seems to be completely surprised by Peter standing there which implies he never saw Peter even after stopping. His window has mysteriously opened immediately.