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)
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.