Seriously - Who Are The Challengers of the Unknown?
After finding out that they aren't on the list to get into the premiere of the latest Batman movie, the Teen Titans use Raven's ability to open a portal anywhere to sneak into the theater and clear some seats by sending the Challengers of the Unknown into another dimension. This sets up two running gags - how ridiculously easy fights would be if Raven didn't keep forgetting about half her powers, and how utterly obscure the Challengers of the Unknown are.
Surprisingly, the Challengers of the Unknown were quite big in the early days of The Silver Age of Comics. Created by legendary comic book writer and artist Jack Kirby, the Challengers were a team of four men who miraculously survived a plane crash unscathed, who sought out new, impossible challenges as explorers and adventurers. The team was popular enough that some speculate it may have inspired The Fantastic Four at Marvel Comics, which utilized the same premise but made one of the four heroes a woman and gave them all superpowers.
The trailers leading into the new Batman movie (which is titled Batman Again) start to get Robin's hopes up about the possibility that he might have gotten a movie based on his exploits. Sadly, the trailers turn out to be for movies based upon Alfred the Butler, The Batmobile and The Utility Belt. To add insult to injury, the entire crowd of superheroes in attendance mock Robin for thinking they'd ever make a movie about a sidekick - even his fellow sidekicks like Kid Flash and Speedy!
Funny as this is, the whole sequence is also a metatexual commentary on how DC Comics can't seem to stop making Batman-inspired movies. Granting that a movie based around The Batmobile is clearly meant to be an exaggeration, it doesn't seem so far fetched given that the trailer for Bumblebee was screened before Teen Titans Go! To The Movies. And with six Joker movies currently in varying stages of production along with Batgirl and Nightwing solo movies, it's fair to say that Warner Bros. has gone batty.
All The Mock Movie Posters
For sheer volume, the single-largest source of sight gags in the movie is the mock posters for various movies based on DC Comics' superheroes. Most of these are seen after Robin leaves the Batman Again premiere and when the Teen Titans are wandering the Warner Bros. movie lot. There are quite a few shots fired at Batman V. Superman: Dawn of Justice, with a Batman vs. Joker movie called "Yawn of Justice" and a Batgirl V. Supergirl poster whose smiling heroines suggest a far-more lighthearted film, where the "V" stands for "Valentine."
There might be a market for Jonah Rex - the tale of a horribly disfigured dinosaur wandering the American West as a hero for hire. There are probably also enough musical fans to justify a Gotham Sirens Musical. The same can't be said for Green Lantern Core, about an apple core that becomes a Green Lantern, or What's Up Doc? starring Doctor Manhattan from Watchmen.
Talking of Watchmen, there's also a poster for a Nite-Owl solo movie, along with posters for The Atom, the Challengers of the Unknown and Wonder Woman along the side of one building in the Warner Bros. lot. There's also a poster for a Detective Chimp movie titled The Case of the Missing Mustache.
Even without the "S" in mustache being replaced with a Superman shield, this would be a clear nod to the infamous issues with the CGI used to remove Henry Cavill's mustache while reshooting Justice League. There's also another reoccurring poster that shows up several times throughout the movie, depicting Cavill with Superman's trademark spit-curl and a mustache.
Related: Henry Cavill's Mustache Explained
All The Superhero Cameos
While most of them don't get speaking roles, virtually all of DC Comics' A-list heroes and quite a lot of the B and C-list show up in the crowd at the Batman Again screening and walking around the Warner Bros. movie lot. All of the core Justice League are in attendance, with Superman, Batman, Wonder Woman, Aquaman, The Flash, Aquaman, Green Lantern (John Stewart) and Martian Manhunter making an apperance. Green Arrow and Black Canary are also there, along with fellow Justice League members Vixen, Elongated Man, Black Lightning, Metamorpho, Red Tornado, Zatanna, Animal Man, Steel, the Ted Kord Blue Beetle, Booster Gold, Shazam and Plastic Man.There's even a few JSA members like Hawkman, Power Girl and The Spectre representing the first superhero team in history.
Looking to the next generation of heroes, you can also spot Supergirl, the Barbara Gordon Batgirl, Speedy (Roy Harper), Aqualad, Kid Flash, Wonder Girl (Donna Troy) and The Wonder Twins, Zan and Jayna. Fans of Young Justice will be pleased to know that Miss Martian, Superboy and Artemis put in an appearance as well. Rounding out the cameos, there are a few odd-ball choices such as Swamp Thing, Detective Chimp, western hero Jonah Hex and Krypto the Superdog. Perhaps the most obscure cameo of all, however, is that of Amethyst - Princess of Gemworld - a fantasy heroine with a solo book from the 1980s.
Lex Luthor, Sinestro and... the Rainbow Raider?
As the Teen Titans ponder how they can earn their own movie, they realize that they lack the one thing every truly great hero needs to be taken seriously - an arch-enemy. After all, Superman has Lex Luthor, Green Lantern has Sinestro and The Flash has... the Rainbow Raider! Yes, the Rainbow Raider - more colorful than Gorilla Grodd and more annoying than The Trickster, he has the power to fly around on rainbow bridges and fire light beams that change a person's emotions. An intelligent criminal might make use of such powers, but Roy. G. Bivolo was kind of an idiot, cursed with a lack of imagination and total color-blindness.
Young Roy was an aspiring artist, held back only by the fact that nobody would buy his paintings because everything was the wrong colors. His father, an optometrist, devoted his life to trying to cure his son's color-blindness and failed miserably, instead creating the goggles that gave Roy his powers. When Roy isn't trying to create perfect forgeries of classic works where the colors are all wrong, he's robbing art museums and destroying classic works so that the only art in the world will be his.
Related: 15 Worst Flash Villains Of All Time
Remember: Deadpool Totally Ripped Slade Off!
Slade (Will Arnett) is quick to point out that he has been around "way longer" than Wade Wilson, when the Teen Titans mistake him for Deadpool. One can hardly blame him for him for being a bit sensitive about the mix-up, as Deadpool was a straight-up rip-off of Slade when he first appeared in New Mutants #98. This was over a decade after Deathstroke The Terminator first encountered the Teen Titans in New Teen Titans #2. Even the names (Wade Wilson vs. Slade Wilson) are a dead giveaway.