Factual error: When Hawkins prepares to leave Princess Gwendolin's chamber, a pet cockatoo sits on a pole near the window. Now how could a parrot native to Australia - or even a "papagei" from South America, as Hawkins intones - appear in medieval England when neither continent would be discovered for several centuries?
Suggested correction: Birds, of course, range widely and flexibly, a storm in the 1800's introduced small African storks to the Americas, Australian birds, to a degree, can be found in Tropical Asia, and therefore could have found their way to Europe via the exotic animal trade (which did well enough for the wealthy at the time),, and the word papagei? Medieval information, and word origins are notoriously fuzzy, ie the first animal to ever be called "penguin" was a similar Northern Hemisphere creature called the Great Auk.
Factual error: At the end of the movie, Lady has four puppies, three Spaniels, like her, and one mixed breed, like Tramp. Realistically, they would all be mixed breed with characteristics from both parents.