Arthur Penn, better known as the Ventriloquist, was the mob accountant to the Penguin, who also shares alliances with Carmine Falcone and Sofia Falcone. During the No Man's Land event, he is seemingly killed off for real, but returns later on in which he is revealed to be the show's version of the Batman supervillain, the Ventriloquist.
Penn worked for Carmine Falcone for many years while he was still the ruling crime lord of Gotham City before eventually retiring to Miami.
When Jim Gordon arrests a criminal carrying one of Penguin's licenses, Arthur Penn visits Harvey Bullock at his office and informs him that Penguin worries about Jim being compliant. However, Bullock tells him that the Gotham City Police Department will honor the licenses.
When Sofia Falcone came to Gotham a few weeks later, Falcone called Mr. Penn and asked him to keep an eye on his daughter. However, Sofia soon found out and threatened to kill him unless he gave her with inside information about Cobblepot's criminal empire.
Arthur Penn informed Penguin that 14 percent of crimes were happening outside of his Pax Penguina. Sofia Falcone then comes in and asks Penguin to come to lunch with her, saying that it would show everyone that he has the support of the Falcone family and could help to get him 100 percent compliance.
Jim visited The Iceberg Lounge, to see if Penguin has any leads on Officer Dave Metzger's murder. Arthur Penn informs Jim that a man named Wally Clarke recently applied for a burglary permit for a butcher shop called The Pork Barrel. Later, Zsasz and Penn present Penguin with evidence that Sofia seems to be up to something behind his back. Penguin tells Zsasz they will "visit" Sofia immediately and find out what she's doing.
The Sirens raid the Iceberg Lounge at the time when Arthur Penn was waiting for Cobblepot to send further instructions. Tabitha Galavan tortures Penn on where Cobblepot is, but is unable to get any information out of him.
As Arthur Penn is at Spa Bo'sh Sumka, Gordon and Bullock head there and find Arthur Penn there amongst the baby-dressed patrons. Penn states that he used to work for Carmine Falcone before his retirement. When he worked for Cobblepot, he had to also work for Sofia Falcone when he was threatened by her. Penn also informed them that he was the one who told Carmine what his daughter was doing. Just then, Sofia shows up with Zsasz, Headhunter, and some unnamed Falcone crime family members, leading to a gunfight between them and Gordon and Bullock. While Sofia fought Gordon, Headhunter and Zsasz chased after Bullock and Penn. After the two of them escaped in Lee Thompkins's car, the Zsasz and Headhunter gave up pursuit and went to get smoothies when they saw the police cars come into view.
After the Cataclysm, Penn stayed in Gotham serving Oswald Cobblepot, counting the reserves and managing the organization.
Arthur went to the territory of the Sirens in search of negotiating with the Penguin, about exchanging food munitions, Angry Tabitha Galavan takes Penn's bullet to kill the Penguin
After not wanting to feed his people enough, Oswald's employees, including Penn, escaped to Haven in the GCPD.
When the gangs betrayed the Penguin, they attempted to sacrifice Penn since Oswald previously sacrificed two Street Demonz thugs, but Oswald unties Penn instead. However, the leader of the gang shoots Penn in the chest. As he lay dying, Penn revealed to Oswald that everyone had left him because they hated him, before passing out in Oswald's arms due to trauma, seemingly dying. He later woke up confused in the morgue.
Penn found the Scarface puppet in a magic shop. His personality had split and he began telling Scarface all about Oswald Cobblepot. Wanting to be the boss, Scarface and Penn went to visit Oswald. The Scarface told Penn to kill Oswald and Edward Nygma, but after Edward told Scarface about his and Oswald’s plan to escape Gotham in a submarine, Scarface decides to spare Edward, but figured that Oswald still had to die.
Oswald tried to get through to Penn, but the Scarface persona continued to lash out at him for how he had treated Penn. Edward then pressed a button that let out a shrill shriek that distracted Penn and Scarface long enough for Oswald to try and wrestle the gun away. Penn and Scarface struggled for the gun, but Oswald got the gun and shot the Scarface puppet’s head off, freeing Penn from it’s influence. However, Penn was then shot and killed by Edward.
- Accountancy: Penn is an incredibly skilled accountant, able to keep track of the finances and transactions of whole criminal empires. He was also given the task of assembling the crime licenses during the Pax Penguina.
- Triple agency: Arthur managed to secretly work for three powerful crime lords at the same time, namely Oswald Cobblepot, Carmine Falcone and Sofia Falcone. He was mainly Penguin's accountant, but also informed Don Falcone about Sofia's actions when she came to Gotham. However, Sofia found out and only let Arthur live when he offered her to be her informant in Cobblepot's crime family. However, Penn was still loyal to Carmine and Penguin, since he informed Don Falcone about Sofia's connection with Professor Pyg and advised Oswald to order a hit on Sofia.
- Network: Due to his history as the accountant of several mob bosses over the course of many years, Arthur has access and connections to various crime families and gangsters. He was the one who put Sofia Falcone in contact with professional contract hitman Lazlo Valentin.
- Survival expert: Penn has wide knowledge of how to stay alive in the mob business, as shown when he offered Sofia to be her informant in the Cobblepot crime family, knowing that she would accept this offer and keep him alive for that task. He is also aware of the fact that a bearer of bad news often gets blamed by crime lords and becomes a victim of 'shooting the messenger', therefore he quickly leaves as soon as he delivers unpleasant information.
- Master tactician: He was capable of hiding his affiliation with Sofia Falcone from experienced crime bosses Carmine Falcone and Penguin. Penn also cleverly tried to eliminate Sofia by proxy by advising Cobblepot to have her killed by Victor Zsasz.
- Leadership: Arthur has at least some rudimentary leader skills, as shown when he managed to organize the remaining henchmen at the Iceberg Lounge during Penguin's absence and ordered them to wait for Cobblepot to send further instructions.
- Ventriloquism: Arthur is a good Ventriloquist as shown when Scarface's personality dominates him.
- Arthur Penn is the show's version of the Batman villain "The Ventriloquist." Prior to FOX giving Gotham Season 5 two extra episodes, producer John Stephens stated that the Ventriloquist and Scarface were cut from the season and will only be alluded to via Easter eggs. The extra episodes allowed them to use Ventriloquist.
- Despite working for Oswald Cobblepot/Penguin throughout season 4 and the beginning of season 5, he isn't portrayed as an antagonist and is simply his accountant, and appears quite timid and harmless. Following his return later in season 5 however, he will appear as a villain when revealed as the Ventriloquist.
- Penn is the fourth Gotham character to be introduced as a seemingly original character in the show, only to be revealed as a canon character from the DC Comics. The previous three are Butch Gilzean/Solomon Grundy, Theo Galavan/Azrael and Nathaniel Barnes/The Executioner.
- Mr. Penn claims to have met Scarface in a magic store, indicating that Scarface may have been haunted, possibly hinting that he may return somewhere down the road in Gotham's canon.
- 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.
- Penn appears to be mostly inspired by Arnold Wesker, the original Ventriloquist in the comics as they are both portrayed as meek accountants with connections to the mob. At one point in "Nothing's Shocking," Penguin accidentally called Arthur, "Arnold", which acts as both a reference to Arnold Wesker and according to Andrew Sellon, a possible indication that Arthur Penn is in fact Arnold Wesker.