Real Name: George "Digger" Harkness
Occupation: Criminal
Marital Status: Single
Base of Operations: Keystone City
Height: 5ft 9in
Weight: 167 lbs
Eyes: Brown
Hair: Brown
First Appearance:Flash #117 (December 1960)
Created By: John Broome, Carmine Infantino

Secretly the illegitimate son of an American soldier and an Australian woman, Harkness was raised in poverty, during which time he developed great skill in making boomerangs, and in using them as weapons. As a young adult, he was hired as a performer and boomerang promoter by a toy company which was, unbeknownst to him, owned by his biological father. Audiences ridiculed him, and a resentful Harkness turned to using his boomerangs for crime.

Although he lacked any actual superhuman abilities, he became a recurring enemy of the Flash, typically by devising altered boomerangs which could produce astonishing effects, and using them ruthlessly. He became a staple member of the Rogues Gallery, a group of villains dedicated to opposing Flash.

Later on, Harkness became a less-than-effective member of the Suicide Squad in exchange for being pardoned for his crimes. However, Captain Boomerang's grating personality and blatant racism (among other things, he constantly referred to another team member, the Bronze Tiger, as an "abo") caused considerable friction among his teammates, and he was considered to be a dangerous, vicious, cowardly and undependable member of the team; dysfunctional even by the Squad's standards.

Amanda Waller, the Squad's commanding officer, characterized Captain Boomerang as "a jerk and a screw-up." This was not an undeserved reputation, as, among other things, Harkness simply watched by as his teammate, Mindboggler, was shot in the back. (Mindboggler had earlier used her mind-altering abilities on Harkness to shut him up when he was verbally abusing another team member.) He also manipulated another team member, Slipknot, into running away from the action just to see if the explosive bracelets the Squad members wore really did activate if the wearer attempted to escape. (Unfortunately for Slipknot, they did.)

While in the Squad, Harkness also briefly took up the mantle of Mirror Master to commit robberies. However, this career was cut short when he was caught and brought to Waller, who put an end to it. She rescinded the benefits Harkness had been given, such as his apartment in New Orleans and his status as a voluntary member of the Squad. Due to various events, Digger once spent year stranded on a deserted island. It was during the series that Harkness revealed a deep patriotism for his home country of Australia. Harkness remained with the Squad until it was disbanded.

Captain Boomerang was killed during the the Identity Crisis by Jack Drake, father of Tim Drake. Digger had been sent by the real killer to attack Jack Drake, only the killer double crossed Digger and sent Drake a warning and a pistol to defend himself. Digger managed to kill Drake but not before he was shot himself.