The addition of Dean Cain and Helen Slater to CBS' upcoming "Supergirl" series continues a trend in superhero adaptations -- the return of veteran franchise actors to new iterations of comic book properties. As fans immediately recognized, Cain and Slater aren't simply two more names added to the upcoming series' cast list. Slater was Supergirl in the character's 1984 solo film, and Cain portrayed the Man of Steel for four seasons on "Lois & Clark: The New Adventures of Superman." Yes, Supergirl and Superman have signed on to star in a new adaptation of Supergirl's adventures, a trend we're excited to see continue.

Of course, Slater and Cain's return to DC lore isn't the first time this has happened. "The Flash," which shares producers Greg Berlanti and Andrew Kreisberg with "Supergirl," previously employed this method by bringing in three actors from the 1990 "Flash" series: John Wesley Shipp, Mark Hamill and Amanda Pays. Shipp, who previously played Barry Allen, now plays the father of the titular hero. Hamill is set to return as a new version of the Trickster, and Pays came back for another appearance as Tina McGee.

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The CW's new "Flash" series didn't have to cast any of these veteran actors in these roles. The producers could have easily cast contemporary stars for these parts. The original "Flash" show lasted only a season a quarter century ago, so getting the actors from that mostly forgotten show doesn't seem like a real big selling point to the uninitiated -- but that's actually what makes the decision to reenlist actors like Shipp and Slater so exciting. It's not being done as an obvious ratings stunt; it's being done to honor the often-overlooked history of comic book adaptations. It conveys that the people in charge of these new projects are true fans, that they're aware of the tradition they're participating in, one that supersedes the allure of hiring Big Name Actors.

That's another difference between now and then -- playing a superhero a few decades back didn't guarantee you the spotlight. Superheroes may be omnipresent now, but that's only been the case for the past 15 years. Before then, adaptations of big name comic book characters were few and far between -- and they were hardly guaranteed success. Unlike their modern day counterparts, though, the actors that played heroes in the '80s and '90s rarely received much attention and success. As mentioned, CBS' "The Flash" couldn't compete with NBC and Fox's Thursday night lineups and tanked after one season. Following "Flash's" demise, Shipp bounced around, from doing guest spots on shows like "NYPD Blue" and "JAG" to repeat appearances on "Dawson's Creek" and "Teen Wolf." Slater's "Supergirl" bombed at the box office, failing to make even half of its budget back. After starting off strong, "Lois & Clark" stumbled hard in its fourth season -- possibly due to a mix of the fallout from a storyline involving frog-eating clones and a disastrous move to Saturday nights. Fast-forward a couple of decades, and peripheral comic characters like the Guardians of the Galaxy are the biggest heroes around, and a divisive reaction from fans couldn't prevent "Man of Steel" from grossing $291 million. Marvel Studios and Warner Bros. have two slates packed with superhero movies stretching out for the next half decade. "Amazing Spider-Man 2," which is considered a critical and financial disappointment, still made over $700 million worldwide.

The bottom line is, we're in the middle of a superhero boom the likes of which we've never seen before. These movies have launched the careers of Chris Hemsworth, Chris Pratt, Henry Cavill and more into the stratosphere. Even if Andrew Garfield never makes another big film, he still has more toys bearing his likeness from two Spider-Man films than Dean Cain does from four years as the Superman. This ubiquity has even extended down to characters like Clark Gregg's Agent Coulson and Hayley Atwell's Agent Carter, both of whom went from supporting roles to leads in their own TV series. Nowadays, if you're associated with a superhero property, odds are you're going to be employed for a while and get to see your face on everything from video games to toys and backpacks. The actors that brought our favorite heroes to life in the '80s and '90s simply didn't see this level of prominence or pop culture dominance. By including them in these new TV shows and films, they get to experience a bit of the zeitgeist firsthand because of new projects, not just the work they did thirty years ago.

Marvel's done a bit of this in the past, most notably through the inclusion of TV Hulk Lou Ferrigno in every one of the jade giant's big screen appearances, but DC is really defining the trend. They've even included overlooked actors from non-DC films -- like Michael Jai White ("Spawn") and Kelly Hu ("X2") -- in "Arrow." This is a fitting development when you think about the attention that DC Comics' has paid to legacy since its launch over 75 years ago. In the comics, mantles like Flash and Green Lantern and Batgirl are handed down from generation to generation, with new heroes taking on the super roles while their respected predecessors retire or stick around with new names -- like Nightwing or Oracle. The casting of comic book veterans like Slater, Cain and Shipp is, in a sense, the real world equivalent of this honored DC tradition, proving that yes, everything old is new again -- and that's a good thing