Continuity mistake: In the episode "FOX-y Lady" (7-10) it was established that Quagmire was 61 years old. In this episode, Quagmire stated to Meg he was bullied in 1986 and a flashback shows that he was a teenager. So how could Quagmire have been bullied in 1986 as a teenager if he should have been in his 30's at this time? (00:12:15)
Continuity mistake: When Stewie is born whilst time is reverting, Doctor Hartman says "It's a girl... with a penis and no vagina". Then after Brian restored the flow of time and Stewie is actually born, Doctor Hartman instead says "It's a boy". (00:18:25 - 00:19:55)
Continuity mistake: When Mayor West panics, Peter shakes him and he falls against a shelf. The plate on the end of the shelf falls off and smashes on the floor. But when Brian points out the gun is there, it is now the middle plate that fell off and the plate on the end of the shelf is intact. (00:15:25)
Character mistake: After Stewie and Brian go to tell the past versions of themselves not to tell 1999 Brian about 9/11, Stewie then finds out that Brian then told 1999 Brian to write the Harry Potter novels. This would have been impossible because the first Harry Potter novel was published in 1997, 2 years before the time period Stewie and Brian arrive in. (00:16:35)
Continuity mistake: There are several differences during the flashbacks and what actually happened. Such as when Muriel is killed Diane appears with everyone else, but in the flashback she appeared moments later. Second, when everyone appears in front of Derek's dead body there are two differences, Tom doesn't say "Dear God!" in the flashback and Diane appears 1 second later in the flashback. Third, Stephanie doesn't say "Did the cork hit me?" when she is shot in the flashback. Fourth, Priscilla isn't wearing a scarf in the flashback even though when it actually happened she was wearing a scarf. Fifth, when Derek says he is going up to the roof he is standing next to Peter and Lois, in the flashback he standing next to Lois and Jillian. Sixth, when Derek leaves the dining room to go to the balcony, no-one is standing next to the door, but in the flashback Diane and Doctor Hartman are standing right next too the door. Seven, when Muriel is killed she is in the middle of a hallway. But in the flashback, she is killed outside Tom Tucker's room.
Other mistake: The guys all go water skiing, towing the boat behind Peter's car. After Quagmire gets his penis bitten off the scene cuts to the hospital parking lot. Quagmire's car is parked next to Peter's. There would be no reason to go home and get his car instead of going directly to the hospital. (00:07:15)
Plot hole: When Stewie and Brian are at the diner Stewie says he negotiated a deal with the mob by telling them he convinced Mort to give him his flash drive with the info to put the mobsters in prison. When they actually meet, Stewie tells the mob guys the flash drive is "his" and that he bought the coverage. Then he says his address is on the drive so they can mail it back to him. The mob guys didn't realise Stewie lied about whose flash drive it really was. (00:15:40 - 00:19:00)
Factual error: In the episode, the Titanic is shown to have sunk the same day it left England. The actual Titanic left England on April 10th and didn't sink until the night of April 14th, almost four days later. (00:11:40 - 00:15:30)
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.
Plot hole: Brian and Peter see Loretta and Quagmire having sex yet, they aren't sure who she's having an affair with. There's no way they couldn't have noticed it was Quagmire - the couch was facing the front door! And obviously Quagmire was on top of Loretta considering the fact that he leans up, says something, then she tells him to get back down here and finish.