Many stories in the first season of the program were based upon book releases from the "Franklin" series. This practice was abandoned entirely beginning with the second season, though some stories still featured minor references to events or dialog from the storybooks.
Franklin is the only character that appears in every single episode.
Franklin is the only one with a real name instead of an animal name, unlike all his friends having animal names, and even if he did, then his animal name would be "Turtle".
Despite being a turtle, he is capable of removing his shell. Real life turtles do not do this as their shell is part of their spinal cord.
According to Nelvana's official website, the character of Badger has been diagnosed with cerebral palsy.