The Gray Ghost, played by Simon Trent, was the eponymous character of an old television show.
Decades later, however, Simon was little more than a washed up, typecast actor. Unable to pay his rent, he slowly sold his Gray Ghost memorabilia to cover the bills, which barely helped him financially. Frustrated with his life, he regretted his decision to ever play his character, destroying the few pieces of the collection he had left.
Soon however, fate, chance or perhaps just very careful planning brought Batman into contact with Trent. After awakening from his tantrum where he broke his remaining Gray Ghost memorabilia, Trent found all the memoriabilia intact again, along with the items he had pawned earlier. They were acquired by Bruce Wayne, who also left a message for Trent that he needed his help. Though he was investigating a bombing spree similar to one depicted in an episode of The Gray Ghost, Batman revealed to Trent the importance and influence the character had on him in his early years. Trent himself, upon seeing the Batman's personal collection of Gray Ghost merchandise, finally understood that playing the Gray Ghost had a significant influence. Trent redeemed himself, donning his Gray Ghost persona once more, and aided Batman in unraveling the mystery of the Mad Bomber. The Bomber turned out to be a toy collector who used Trent's memorabilia to re-enact the events in the episode of The Gray Ghost in order to pressure Gotham into giving him millions of dollars, only for the Gray Ghost to sabotage the effort and Batman brought him to justice. After the incident reached the newspapers, the Gray Ghost was thrust into the spotlight for his role in capturing the Mad Bomber, causing a resurgence of popularity for his show. Shortly thereafter, a major home video release of the long lost TV series was made from Trent's personal film collection, restarting his acting career and making him a wealthy man. During a public video signing in costume, Bruce Wayne acquired Trent's autograph and subtly revealed to his hero his own secret identity as Batman, which pleased Trent to no end.
The Gray Ghost is voiced by Adam West, the actor who played Batman in the 1960s TV series and associated movie. Bruce Timm and Paul Dini have stated that they would not have made the episode in which he appears if West had turned down the part as they feared he would be offended by an animated parody of the typecasting he reportedly suffered in his later career. West, however, was happy to voice the character.
Adam West voiced a similar character on Disney's Kim Possible: a retired crime-fighter called "The Fearless Ferret". His costume is adopted by Ron Stoppable, voiced by Will Friedle, the actor that voiced Terry McGinnis.