Alexander Graham Bell is depicted as having an American accent. While he lived in the United States for many years, he was born and raised in Scotland.
Although Bell is credited with inventing the telephone in 1876, his patent application arrived after a telephone patent by Elisha Gray (by a matter of hours) although Bell's lawyers pushed for his application to be recorded first. Similarly Antonio Meucci has also been working on a telephonic invention in 1871, although it used a different method than Gray's and Bell's inventions. Had Bell not invented the telephone, Gray's invention, with the backing of the Western Electric Company, may have taken hold in the same way.
In the closing scene outside the farmhouse in 1890, a truck can be seen coming down the hill in the upper right hand corner.
Set in 1875, Jeffrey and Bogg need to get Alexander Graham Bell and Mabel Hubbard together as they haven't begun dating, but in reality, they started their relationship in 1873. They would have had to use the Omni to go back two years earlier to set history right.
In the street scene where Bogg saves the girl, two guys in blue jeans and t-shirts can be seen in the back ground behind Jeffrey.
At the restaurant, Phineas looks down while speaking to Mabel so she wouldn't be able to see his lips moving well enough to read them, but she is able to respond appropriately.