Continuity mistake: When everyone is in the dining room at the dinner table, the order of where everyone sits changes between shots. In all moments where it shows everyone sitting, the order is Priscilla, Derek, Jillian, Mort, Muriel, and Carl. But in one shot, the order is Priscilla, Derek, Jillian, Muriel, Mort, Carl.
Continuity mistake: When Derek Wilcox is killed and on the ground, he is on his front with his head turned. He got hit above his right eye and blood is coming from underneath him, but after everyone else arrives outside, he is on his back with the wound above his left eye and blood is all over his face.
Continuity mistake: Just after the guests have found Muriel, there is a shot from outside the manor where we can see Quagmire's car at the back of the rest of the cars. But in the next overview shot of the manor, Quagmire's car is now in front of a red car.
Continuity mistake: When Brian and Stewie arrive in Leonardo's atelier we know that they are in Florence for two reasons: because of history and because we see Palazzo Vecchio (which is in Piazza della Signoria, in Florence) outside the window. Then when Stewie and Bertram are fighting with Leonardo's flying machine the city of Florence is wrongly represented as if it was Venice, with the see, the lagoon and the canals.
Continuity mistake: When the guests walk through the secret passage, the order of the guests change between shots. First, it's Peter, then Chris, then Carl, then Doctor Hartman, then Seamus, then Quagmire, then Lois. But in the shot of the passage, the order is Peter, then Chris, then Carl, then Lois, then Consuela, then Doctor Hartman. Then when they reach the secret room, the order is Peter, then Chris, then Carl, then Lois, then Bonnie, then Quagmire, then Derek, then Jillian.
Continuity mistake: Peter knocks out Joe during the search in the hallway. Yet when everyone is fighting about the motives, there is a wide shot of the fight but Joe can be seen fighting behind a couch with Doctor Hartman and Derek. He can't have regained consciousness, because he doesn't regain consciousness until later in the episode.
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.
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.
Continuity mistake: When Muriel Goldman dies, everyone gathers up around her. When that happens, you can see Tom Tacker and Meg in the background, although they both disappeared a few scenes earlier. And than when everyone gathers downstairs, they do a body count and discover Tom and Meg are missing and only then are they found.
Continuity mistake: When Peter returns home from being hyped up on Red Bull, he has numerous cans in his arms. When he sees Stewie he immediately drops the cans on the floor but when the camera pulls back as he sits down with Stewie in his lap, the cans of Red Bull are nowhere to be seen.