Plot hole: When it is revealed that Chris's teacher was never born, Teacher Doug introduces himself, despite the fact that if Chris's teacher was never born, Doug would already have been teacher for the entire year, and therefore all of the students should know him and he would not have to introduce himself.
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)
Factual error: They all go back to 1912 in London. When Stewie gives a street performer money, Brian informs him that the person wasn't Charlie Chaplin but in fact, Adolf Hitler, and he was right. Back in 1912, Hitler was living in Vienna, Austria and was poor after failing to get into art school. He didn't actually leave the country until 1913 when he moved to Munich, Germany. (00:10:20)