The entertainment market is bursting at the seems with superhero movies and TV shows, the genre has never been bigger. However, before the success of the MCU — which brought about this superhero film/TV renaissance — there were still some pretty successful superhero franchises out there. From the original Superman films to the '77 Hulk TV series, there are a lot of actors from previous comic book adaptations who have made their way into the reboots of these franchises. DC is definitely the master of these easter egg castings, but Marvel and other franchises have had their fair share of cameo roles.

RELATED: The 1997 Justice League Of America TV Pilot: Where Are They Now?

Some might argue that these cameos are just for nostalgia value, just a way to get lovers of the original to watch the reboot. We would have to disagree, we think it's a great way to connect a reboot to its roots. In fact, the more the merrier, and it's surprising that the MCU hasn't done this as much as DC franchises. Regardless, when a superhero franchise brings back one of the stars of the original movie or TV show, it's always a nice nod. So, which are some of the coolest callback cameos? CBR's got 15 of them for you right here!

15 ADAM WEST - THE GREY GHOST

Adam West, who sadly passed in early 2017, is without a doubt remembered as the most iconic Batman actor of all time. The '66 Batman TV series was wacky and zany and campy, but it's remembered fondly by fans both old and young. After Batman, Adam West would go on to do quite a bit of voice work in his later years, usually playing a fictional version of himself or some sort of similar character.

There is one voice role stands amongst the rest, his guest appearance on Batman: The Animated Series. Like many of his voice roles, West played a character similar to himself, Simon Trent, an actor who got typecast after playing "The Grey Ghost" on TV for so long. Trent finds a new lease on life after working with Batman, who reveals the Grey Ghost to be his childhood hero; a fitting tribute to the Batman actor.

14 MARK HAMILL  - THE TRICKSTER

Mark Hamill is best known for two roles, Luke Skywalker and The Joker. However, Hamill has also portrayed another clown-like villain from the DC universe, The Trickster. Somewhat of a ripoff of The Joker, the first Trickster, James Jesse, was a Flash villain that first appeared in 1960 and has been played by Mark Hamill in every Television appearance thus far. Hamill first played The Trickster in the 1990's The Flash TV series and has since reprised the role at every corner.

Hamill voiced The Trickster in Justice League Unlimited, where he portrayed the character as a victim of his own psychosis. Hamill also voices the character on Justice League Action, but his greatest reprisal came a bit earlier on the first season of CW's The Flash. Hamill reprised the role of The Trickster in the episode "Tricksters" where he teamed up with the second Trickster, Axel Walker.

13 CHRISTOPHER REEVE - DR. VIRGIL SWANN

Many still consider Christopher Reeve to be the best Superman actor of all time, and we're inclined to agree. It was an absolute tragedy when the man who the world saw as Superman suffered an accident and could no longer walk. This tragedy was made worse when Reeve fell ill and passed in 2004. However, while Reeve was mainly a medical research activist after his accident, he did have one significant acting role in Smallville.

On Smallville, Reeve Portrayed an original character named Dr. Virgil Swann, a scientist who told Clark of his alien origins. Swann translated a Kryptonian message that told him of Clark's Kryptonion name and origins, informing him of the destruction of his home planet. Series developers Alfred Gough and Miles Millar had planned to have Reeve on from the start, creating the Dr. Swann character just for him.

12 JOHN WESLEY SHIPP - DR. HENRY ALLEN

In 1990, CBS released a Flash TV series starring John Wesley Shipp as Barry Allen. The series was a display of modern (at the time) special effects and costuming and was nominated for two Emmys. Despite it's popularity, the show was cancelled after one season, but it wouldn't be the last time Shipp played a member of the Allen Family. In one of DC's many "former version" cameos, Shipp was brought on to CW's The Flash as Barry's Father, Dr. Henry Allen.

Shipp not only looks like he could be Grant Gustin's father (a happy coincidence), but he also portrays the character perfectly for the series. Though Henry is killed in season 2, Shipp still guest stars as the Earth-2 version of Henry Allen named Jay Garrick. If that name sounds familiar, it's because Jay Garrick was the original golden age Flash, another fitting tribute role for the character.

11 LYNDA CARTER - PRESIDENT MARSDIN

Another actor who is considered the best depiction of a superhero is Lynda Carter, the original Wonder Woman. Carter portrayed the princess off the Amazons from 1975 till 1979, a role that is considered by many to be a perfect and iconic adaption of the character and comics. The talented actress' depiction of the character inspired many as time went on, including Wonder Woman director, Patty Jenkins.

Though Carter's touring schedule — she's also a very talented singer — unfortunately restricted her from having a cameo in Wonder Woman, she has cameoed on another DC show; two in fact. Carter had a brief role on Smallville as Moira Sullivan and currently has a recurring role on Supergirl. Fitting to the strong and powerful woman that Carter is, the actress portrayed U.S. President Olivia Marsdin on three episodes of the show.

10 LOU FERRIGNO - VOICE OF MCU HULK

At the time of the 1977 CBS series The Incredible Hulk, special effects were nowhere near what they are now. So, instead of making a computer-generated green monster, the Hulk was created by covering a body builder in green body-paint. Sounds a bit old-fashioned, but it got the job done, especially since Lou Ferrigno made an amazing Hulk. Ferrigno played The Hulk for five season and three TV movies of The Incredible Hulk, later reprising the role for various other incarnations of the character.

Before the MCU's The Incredible Hulk, Ferrigno had a brief cameo as a security guard in 2003's Hulk. In the MCU reboot, Ferrigno once gain cameoed as a security guard, but this time he also provided part of The Hulk's voice in the film. Ferrigno continued to voice The Hulk in every MCU appearance thus far, including the upcoming Thor: Ragnarok.

9 DEAN CAIN - JEREMIAH DANVERS

Lois & Clark: The New Adventures of Superman was a bit of a departure from previous incarnations of the character. The show was meant to explore the romantic relationship between Lois Lane and Clark Kent, their screen time equal to Clark's adventures as Superman. The show also integrated a more lighter-hearted, humorous tone to the depiction of Superman. Starring Dean Cain, the show went on for four successful seasons.

Dean Cain's career has been a bit sparse after Lois & Clark, but Cain has had a few appearances on other Superman-related shows. Cain had a single-episode appearance on Smallville as Curtis Knox, an immortal doctor who harvested parts of Kryptonite-infected metahumans. Cain has a bigger part on the Superman-adjacent series Supergirl as Kara's adoptive father, Jeremiah Danvers.

8 TERRI HATCHER - RHEA, QUEEN OF DAXAM

Speaking of Lois & Clark, Teri Hatcher starred alongside Cain as Lois Lane. Hatcher portrayed the strong and defiant reporter for all four seasons, and the show helped launch her future career. After starring in the James Bond film Tomorrow Never Dies, Hatcher had a long career starring on Desperate Housewives. Two of Hatcher's more recent roles are nods to her early role as Lois Lane.

Not only did Hatcher portray Lois Lane's mother on Smallville (continuing the trend of a former Lois Lane actor coming back to play the character's mother) she also had a recurring role on Supergirl. On the CBS-turned-CW show, Hatcher portrayed the original character, Rhea, Queen of Daxam, an alien world that was at war with Krypton. The character is also the mother of series regular Mon-El.

7 ROB PAULSEN - DONATELLO

One of the most, if not the most prominent voice actors of all time is Rob Paulsen. The voice actor has portrayed at least one of your favorite characters, starring in everything from Animaniacs and Pinky and the Brain to Ben 10 and Danny Phantom. One of Paulsen's earliest iconic roles was as Raphael in the original Teenage Mutant Ninja Turtles animated series. The 1987 series was much more kid-friendly and comedic than the original comic, and Paulsen portrayed hot-headed Raph in a rather humorous way.

Paulsen's role as one of the turtles came full circle when he returned for the 2012 series. However, Paulsen didn't come back to play Raphael, instead he was cast as Donatello. This change wasn't difficult for Paulsen — a seasoned voice actor with a huge range — who easily shifted from portraying a hot-head to a gear-head.

6 POWER RANGERS CAMEOS

The Power Rangers series features an insanely dense narrative born both out of a connected timeline and a complicated story spliced together from Japanese footage of the original Super Sentai series. Most Power Rangers series are in canon with the original Mighty Morphin show, each new team acting as legacy characters to the previous. In various instances some of the original actors for the first team of Power Rangers have come back to once again portray their character.

Two of the most prominent returning characters are Kimberly Hart, the original Pink Ranger, and Tommy Oliver, the Green Ranger. The characters were portrayed by Amy Jo Johnson and Jason David Frank respectively and throughout the show, the two characters developed a romantic relationship. Frank has returned to the franchise much more than Johnson, but both had a brief cameo in the 2017 Power Rangers reboot film.

5 HELEN SLATER - ELIZA DANVERS

The very first superhero film with a female lead was 1984's failed Supergirl movie. Some might not know that the film was meant to serve as a spinoff to the Christopher Reeve films, Marc McClure even reprised his role as Jimmy Olsen in it! The film might be canon with the rest of the Superman films, but it is usually looked over or forgotten by both WB and Superman fans. The film starred Helen Slater as the titular character, but it wouldn't be Slater's last DC role.

Slater had a recurring role as Talia al Ghul in Batman: The Animated Series for four episodes of the beloved series. The actress would have a more direct connection to her Supergirl role by playing the character's aunt, aka Superman's mother, Lara-El on Smallville. To bring it all full circle, Slater currently portrays Supergirl's adoptive mother, Eliza Danvers on Supergirl. 

4 LARRY KENNEY - KING CLAUDUS

Thundercats is one of the most beloved cartoons of the '80s, perhaps one of the most beloved period. The show followed the titular Thundercats, cat-like aliens who land on Third Earth after their homeworld was destroyed. The Thundercats were led by Lion-O, a child in the body of an adult (due to a suspension capsule malfunction) who was voiced by Larry Kenney. The original series ran for four seasons and was eventually rebooted in 2011.

The 2011 reboot of Thundercats was, unfortunately, canceled after its first season, but it did manage to give a nod to the original during its brief time on the air. While veteran voice actor Will Friedle (Batman Beyond, Kim Possible) played Lion-O in the reboot, Larry Kenney did come back for a nice cameo role, portraying Lion-O's father, King Claudus.

3 ANETTE O'TOOLE - MARTHA KENT

In the critically panned Superman III Anette O'Toole portrayed Clark Kent's high school love interest Lana Lang. In the film, Lana sees Clark at a high school reunion and starts to get back in touch with him while her ex-husband vies for her attention. O'Toole hasn't been in much since, but is more recently known for playing Martha Kent on Smallville.

Though Martha's role in Smallville got smaller and smaller over the years, O'Toole played the role brilliantly, even things got weird in the later seasons. The actress still gave the role her all even when she only had brief appearances in later seasons. Funnily enough, O'Toole's casting was not intended to be a nod to her former Superman role, since the developers of the show had no idea she played Lana Lang until after she had the part. Just a happy coincidence, we guess.

2 TERENCE STAMP - JOR-EL

Terence Stamp first portrayed General Zod in the opening sequence of the first Superman film. During his trial, Zod is found guilty and sentenced to the Phantom Zone. Before being banished, Zod curses Jor-El and swears he will get is revenge. Stamp reprised the role in Superman II, wherein Zod eventually gets his revenge on the house of El. Stamp was known for brining a fierce and intimidating portrayal to General Zod.

Terence Stamp, with that incredible voice of his, eventually found his way back into Superman lore in a recurring role on Smallville. Stamp voiced Jor-El in the series, acting as a disembodied voice that guides Clark as he learns and grows with his powers. Jor-El directs Clark to the stones that eventually form his fortress of solitude, where Stamp's voice is depicted as an AI of Jor-El.

1 AMANDA PAYS - TINA MCGEE

Much like the modern Flash series, the original 1990 series didn't just follow Barry Allen on his own, he had friends helping him along the way. In the CW show, it's his team at S.T.A.R. Labs, and the original series was pretty similar. John Wesley Shipp's Barry Allen/The Flash was assisted in his crime-fighting adventures by S.T.A.R. Labs scientist Christina "Tina" McGee, played by Amanda Pays.

Amanda Pays, in the weirdest/coolest cameo casting on this list, reprises the role of Tina McGee in CW's The Flash... sort of. Pays plays a different version of Tina, an employee of Mercury Labs, rival to S.T.A.R. Labs. It is even implied that this Tina is an alternate universe version of the original, since the show has explored alternate Earths and the like.

Can you think of any other instances where former superheroes had cameos in modern reboots? Let us know in the comments!