The comic book character Ace the Bat-Hound was the canine crime-fighting partner of Batman and Robin in DC Comics of the 1950s and 1960s.

Biography

Pre-Crisis
Ace was a German Shepherd originally owned by an engraver named John Wilker. He was found by Batman and Robin after his master was kidnapped by a gang of counterfeiters. Batman used Ace to try to locate Wilker. Because he had already placed a large number of "lost dog" announcements for Ace in his civilian identity of Bruce Wayne, he was concerned that anyone recognizing Ace (who had a prominent star-shaped marking on his forehead) might make the connection between Bruce Wayne and Batman. To forestall that problem, he hastily improvised a hood-like mask for the dog that incorporated the bat emblem as a dog tag dangling from Ace's collar. Ace was subsequently christened The Bat-Hound by a criminal the dog helped Batman to apprehend.

Wilker later took a new job that made it difficult for him to take care of Ace, so he left the dog to Bruce Wayne. Wilker was never aware that Ace was the Bat-Hound or that Bruce Wayne was Batman.

An early case involved Ace tracking down a mentally ancient weapons expert who was using his own weapons to commit crimes. At one point, Ace acquired super-powers thanks to Bat-Mite but this was short-lived. He did have his own training. For example; his specialized radio collar, when activated told him to don his own mask (via a hands-free device) and track down Batman and Robin. Ace was used less and less over time, and for various reasons. When Bruce was overcome with night terrors, Robin suggested Ace sleeping aside him.

Ace disappeared from the Batman comics after Julius Schwartz took over as editor in 1964. His last appearance was a cameo in a story where Batman had lost his fighting spirit. Ace made only very occasional comic book appearances in the years afterward.


Post-Crisis
A version of Ace is seen in the cosmic realm Limbo when the hero Animal Man takes a trip through it.

A modern-day version of Ace was reintroduced in Batman #462 (June 1991), although he has been rarely seen in recent years. This version was originally a guide dog belonging to a blind Native American named Black Wolf, who called him "Dog". The dog assisted Batman in fighting criminals from Black Wolf's tribe. Following Black Wolf's death, Batman adopted Dog, renaming him Ace.

He did not wear a mask, nor was he ever referred to as Bat-Hound, and has the appearance of a beagle-pug crossbreed (which exists in the real world as a puggle) with a bat-shaped dark patch on his flank. Ace has at times helped Batman on cases and is depicted to be very affectionate towards his owner and vice versa.

After Batman is disabled by the villain Bane, Azrael takes over the role and ejects Ace, Nightwing, Robin and Harold Allnut from the Batcaves. Harold, a trusted confidante of Batman, takes in Ace; they live in a part of the caverns Azrael is unfamiliar with. To keep busy, Ace enjoys playing with a robotic mouse built by Harold.

Ace disappeared without explanation after the events of the No Man's Land storyline in the late 1990s. He cameos in Ambush Bug: Year None.

A traditional Ace was seen in Final Crisis: Superman Beyond 3D. He is in limbo with other "forgotten characters", such as Gunfire, Geist, Hardhat of the Demolition Team and Merry Man of the Inferior Five. Merry Man explains everyone is here where no stories exist because nobody is writing about them. Despite this, Superman and his allies work to rescue all the residents of Limbo, who then help assist in the battle against the cosmic threat of Mandrakk.

The original Ace appeared in a flashback scene in Batman Inc. #4, thus making the current canon status of the Post-Crisis Ace unclear. In this story, Ace is trying to play with Robin who is fuming over Kathy Kane, Batwoman, and her influence on Batman.


The New 52
In Batman and Robin Vol 1: Born to Kill as part of The New 52 (a reboot of the DC Comics universe), Bruce is seen purchasing a black Great Dane from a kennel. He later gives this dog to his son Damian who names him Titus, though writer Peter Tomasi stated in an interview that he considered naming the dog Ace. Damian rejects the dog at first, but eventually bonds with the dog and names him Titus.