The character also appears in Arrow's tie-in novels and digital comics, as well as the Lego Batman 3: Beyond Gotham video game.

In February 2012, David Ramsey was cast in the pilot episode of Arrow as John Diggle, a "former military man now working as a bodyguard for hire who soon finds he is trapped in a battle of wits, loyalty and trust".

He further explained that Diggle's mutual abilities were a means of setting him up early in the series as a confidant for Oliver's vigilante persona.

[3] Ramsey enjoyed the fact that he did not have to worry about matching the comic books, saying, it allowed him to "just kind of take [his character] and run with it".

[4] David Ramsey has compared Diggle to Alfred Pennyworth from the Batman comics, describing the character as Oliver's "moral voice".

"[5] He has stated that since Diggle is older than most of Team Arrow and, to an extent, more experienced on the field and reconnaissance fighting, the other members "look to him for some leadership".

[9] A running gag is that Diggle, whenever taken suddenly to places by Barry Allen / Flash at super-speed, vomits as a result of motion sickness,[10] an exception being in the Arrow season 6 episode "The Devil's Greatest Trick".

[11] Diggle's military career and heroism led some fans to draw comparisons between him and Green Lantern John Stewart.

"[16] Diggle, alongside Felicity, is shown to play an important role in the transitioning of Oliver from a 'lone-wolf' to part of a vigilante team.

Club stated "Amell, Ramsey, and Rickards have the kind of lightning-in-a-bottle chemistry that makes all their scenes together hum", in her review of the first half of season 2.

He is hired as the bodyguard of billionaire Oliver Queen by his mother, Moira[37] and later becomes his confidant in his mission to save Starling City.

When Oliver is presumed dead at Ra's al Ghul's hands, Diggle leads Felicity, Roy, and Laurel Lance until his friend's return.

After Oliver's return, Diggle accompanies him to Nanda Parbat to help him free Malcolm Merlyn, but the two are captured.

[48] Now going by the codename "Spartan",[49] he discovers that the organization that targets the newly named Star City is H.I.V.E., who had hired Lawton to murder Andy.

Guilt-ridden over his brother's role in causing Laurel's death, Diggle seeks revenge against Andy and Darhk.

He initially lies to Lyla that he killed Andy in self-defense, but Oliver encourages Diggle to admit the truth to his wife.

Due to the events of The Flash episode "Flashpoint", Diggle's family history is altered: his daughter Sara has been erased from existence and replaced by John "J.J." Diggle, Jr., as a result of a timeline change caused by Eobard Thawne, correcting the Flashpoint reality created by Barry Allen.

However, Andy's betrayal and death at Diggle's hands has taken a toll on him; he struggles to control his rage and occasionally pulverizes criminals to vent it, fueling Oliver's concern over his erratic behavior.

[60] In season three of The Flash, Diggle joins forces with other superheroes to stop an alien invasion, while he learns of the alteration of his life with Lyla, his daughter's erasure and his son's status as a time aberration, and despite the hurt caused by these circumstances, he chooses to forgive Barry.

[62] However, he was wounded by bomb shrapnel and suffers a degenerative nerve injury that affects his motor control that requires taking daily medications, resulting him to develop a drug dependency.

After Oliver decides to remain being the Green Arrow, Diggle accepts the job offer from Lyla as one of the commanding officers in A.R.G.U.S., using his new position to lead his subordinates to maintain order in the city's police's place due to them having been compromised by crime lord Ricardo Diaz.

Despite succeeding, the trio are arrested for violating the city's anti-vigilante law, but mayor Emily Pollard ultimately offers to drop the charges against them, provided they agree to be deputized and work for the police, as Oliver has.

The two make amends when Diggle learns that his father died because of his own negligence and Stewart is the reason anyone survived the operation.

[73] After Team Arrow thwarts the Ninth Circle's plan to destroy Star City, Diggle takes Oliver and a pregnant Felicity to an A.R.G.U.S.

[76] After the adult Connor is accidentally teleported from 2040 to 2019 with Oliver's children, Diggle is shocked and devastated to learn that J.J. is psychopathic and becomes Grant Wilson's protégé and successor as Deathstroke and kills Rene's daughter Zoe in the future.

[78] In season six of The Flash, Diggle arrives in Central City to give Barry the mask he gave Oliver the first time they met.

Diggle convinces Barry to go to 2049 to check on his daughter Nora, but he is knocked out of the Speed Force by Godspeed drones.

assignment in Gotham City, Diggle encounters Luke Fox in a bar where he got involved in a poker game with Russell Tavaroff.

While comparing to how they both lost their fathers, Diggle advises Luke to take the right path as they notice the Bat-Signal giving off a Morse code.

[82] After a while, Diggle assists his old friend Jada Jet into finding Joker's joy buzzer that would be used to help treat Marquis.