Andrew Sellon is a ventriloquist in real life, something which the producers weren't aware of when he was hired for the show.
The supervillain Jane Doe debuts. In the comics, Jane Doe is an Arkham Asylum inmate who stalks people, learns everything about them, murders them, and steals their identity, disguising herself and living as them, this version has shapeshifting powers as the result of being experimented on at the Indian Hill.
Penguin mistakenly calls Arthur, "Arnold," which was the real name of The Ventriloquist in the comics, Arnold Wesker.
Arthur Penn reappears and is revealed to be the Batman supervillain The Ventriloquist. Originally, his role as Ventriloquist was going to be cut from the season due to it being shortened. However, FOX was granted two extra episodes in season five, which allowed the producers and writers of the show to go ahead and use Penn as the Ventriloquist.
Penn's Scarface personality appears to be a manifestation of his repressed anger toward Oswald Cobblepot, which reached its climax when he was left for dead in the morgue.