Other mistake: Towards the end when Janet, Brad, Oliver and Betty are singing "We're going to do it anyhow," as they are dancing down the aisle, Betty very visibly trips and grabs Oliver to stop from falling over.
Other mistake: After Leonardo sets up his canvas to begin painting The Last Supper with Jesus with his disciples, he says "hold it" and then the camera flips to show the men (and Comicus) now situated behind the table. Look at the disciple in the blue tunic at the right, who first looks off to his right, then corrects his position, and faces left, with his arms extended. (00:52:32)
Other mistake: He says his father won the sculling 1928 Olympics, which doesn't match up with their ages.