This is the story of the Fastest Man Alive, The Flash from the DC Animated Universe.
Origin[]
Wally West was a science assistant. A freak accident would give him super-powers when a lightning bolt struck him, but the chemicals beside him at the time stabilized him and made his body start moving at lightning speeds. The bolt would link him to the primordial power of The Speed Force, which gradually increase his speed even faster than lightning.
Superman: The Animated Series[]
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Superman and the Flash race each other in the latter's debut.
Flash appeared in one of the precursor series to Justice League, Superman: The Animated Series, in the episode Speed Demons. In the episode, Flash and Superman race each other to prove who is faster, partly out of an amicable rivalry, and partially for a charity event. The devices hooked up to them to keep track of their positions for the race also used their kinetic energy as a power-source to empower the inventor, Mark Mardon, who would take on the name "The Weather Wizard". Weather Wizard uses the kinetic energy to power a scepter which could theoretically, generate natural disasters - as it turned out, the experiment worked. Weather Wizard's use of the scepter gets Superman and Flash's attention, and when the disasters target their exact location, Flash and Superman figure out their trackers are to thank, destroy them and team-up to find and defeat Mardon. By the end of the episode, with Weather Wizard defeated, the two superheroes race once more, purely for the sport of it.
Justice League (2001)[]
Secret Origins[]
The Flash saves Green Lantern from the Imperium.
In the Justice League episode Secret Origins, Flash meets Superman again when dealing with an alien invasion. An alien race hive-mind known as the Imperium invade Earth. Flash meets Superman at the invasion point but also comes across an powerful warrior-woman going by the title Wonder Woman, a winged-warrior named Hawkgirl, a native from Mars, and a soldier returning to Earth after being recruited to the Green-Lantern Corps - an intergalactic law-enforcement agency. Flash, Superman, Wonder Woman and the Green Lantern would fight the creatures on the outside while the masked detective, Batman helped break-out a captured resident of Mars - the Imperium's previous victims, on the inside. The six heroes would manage to save the planet on a scale none had thought possible solo. As a result, they decide to form a regular team - the Justice League.
War with the Justice Lords[]
After aiding the Justice League in preventing many other world endangering-level threats, Flash discovers that he is an essential part of the League in a bigger way than he thought when they are visited by alternate versions of themselves from another universe.
As it turned out, their alternate counterparts, called the Justice Lords, are evil versions of the league when in their universe, their Lex Luthor is elected president of the United States and killed their Flash, resulting in Justice Lords Superman killing him and taking over the world. After being tricked into going the alternate universe and getting locked in cells that neutralize their powers, Flash manages to escape, free his teammates, and with the surprising help from a now-reformed Justice Lord Batman, they return to their universe to deal with the rest of the Justice Lords.
The Flash holds his ground against Justice Lord Superman.
Confronting the Justice Lords in an prison where the mainstream Lex escaped, Flash fights with the evil Superman when the original Superman is absent, upon being backed into a corner, Flash tries (and sadly fails) to get through to Lord Superman, but just as he's about to get killed, Superman arrives with the mainstream Lex and with an energy disruptor, he takes away the lords powers, rendering them powerless,
Afterwards the league takes their evil doppelgangers away, but not before Lex mentions taking an interests in politics.
The Thanagarian Invasion[]
Eventually, Hawkgirl's people; the Thanagarians, came to earth claiming that their enemies, the Gordanians, are coming to earth to conquer it and offer to make a force-field around the earth to protect it. Unfortunately, the Thanagarians reveal that they plan to conquer earth and use it as a portal to their homeworld, destroying earth in the process. Not wanting that to happen, Flash and the league attempt to stop them, but they fail and successfully invade earth.
When the League decides to hide out as civilians to avoid being captured, Flash retaliates as he's still keen on keeping his identity secret; Until Batman reveals he already knows everyone's identities, pairing up with Green Lantern and head back to Gotham city.
Coming with Batman to the Watchtower, Flash and Batman hijack it back under their control, but is surprised when he is locked in an escape pod by Batman, while he pilots the base directly towards the gate, destroying it in the process.
In the aftermath, Flash votes that Hawkgirl stays with them while Wonder Woman (completely hurt with her betrayal) votes against, but Hawkgirl, with a heavy heart, announces her official resignation from the league.
Static Shock[]
Flash makes his appearance, saving Static and his genius partner Gear from a supervillain ambush.
Sometime prior to the Thanagar war, Flash was with the members guarding a left-over module of the evil computer virus Brainiac when a cosmic storm hits the watchtower, knocking them out of orbit & shutting down most of the power, with no other options to recharge the core available, Batman suggests getting the help of the young lightning-hero, Static.
After saving Static and his genius partner Gear from a supervillain ambush, Flash and the rest of the league bring them to the watchtower for Static to recharge it, when all of a sudden, they are called to faraway distress call and decide to leave the two heroes in charge. Unbeknownst to them, Brainiac (who escaped into the computer system during the blackout) faked the call to obtain complete control of the watchtower to destroy the earth.
Fortunately, Static and Gear are able to alert the league in time for them to help the dynamic duo rid the watchtower from Brainiac's control and get it back online. However, during the fight, Brainiac had gotten inside Gear's backpack and when Flash checks on the boy, he's shocked to discover that Brainiac assimilated him and he, along with the rest of the league are followed shortly thereafter.
Static, being the only one left evades the League and frees them from Brainiac's control (dealing with Flash by magnetizing him to the ground), and with their help, Flash and the rest are able to foil Brainiac once again, afterwards, Flash congratulates Static for his heroic efforts and says he'll be a fine member when he's old enough to join the League.
Justice League Unlimited[]
Feud with Cadmus[]
Sometime after Hawkgirl's departure, Flash and the rest of the League decide to expand their operations and recruit other superheroes into the league, with some of those new members including the king of Atlantis Aquaman, the masked detective The Question, and the Robin Hood-themed archer Green Arrow. Unfortunately this act was enough to make the governments of the world turn to the organization CADMUS (originally formed when Superman was brainwashed) for more "loyal" aid, as Luthor told them everything about the Justice Lords incident and made them fear if the Justice League did the same.
Other Heroics[]
The Flash reluctantly rushes into Kalibak's cell and rescues him.
After the Justice League expanded, Flash devotes more of his time to protecting Central City, instead of participating in League activities on a full-time basis. Nonetheless, he is still sitting alongside his fellow founding members in providing oversight to the new, larger Justice League, and is involved in many of their operations. For example, Flash assists Big Barda and Mr. Miracle in freeing the latter's mentor, Oberon, while preventing a takeover of Apokolips that would have eventually led the planet to become a threat to Earth once again. When Hawkgirl returns, Flash tries to help her make peace with their team members, mainly with Wonder Woman.
Dealing with Lex's endgame[]
Unaware on both sides, Lex is playing both sides against each other to not only ultimately achieve "Godhood", but to also ruin Superman's reputation and claim dominion over the world by secretly being benefactor for CADMUS by giving them enough money for them for projects of creating Genetic clones of superhumans, but are completely loyal to the government.
The second part of Lex's plan is him "running" for president just like his alternate counterpart, which was enough make Superman paranoid enough to destroy a kryptonite-powered devise that was beneficial for society. When the Question confronted Luthor about this, he revealed that he faked his entire election campaign knowing it will make Superman paranoid, and he makes the Justice League surrender themselves to the government by hijacking the watchtower's cannon and fires it as a CADMUS-themed building, which also makes the Director of CADMUS, Amanda Waller, order their army of genetically-cloned super-humans to attack the Watchtower.
After finishing building an android body with all the League's powers for himself to upload his DNA in, Lex is confronted by Batman and a now-convinced Amanda Waller to stop him, but just as Flash and the rest of the league arrive, Lex is revealed to be a host body for Brainiac.
Stopping Brainiac/Luthor[]
Now revealed, Brainiac/Luthor escapes and, after following and agreement with Lex, they agree to become one where Lex uses this opportunity to become to God he so wildly sees himself as. With all the extra members tired from an attack by the clones, Flash and the founding members follow Brainiac to his location where they witness Lex and Brainiac fully fuse into one.
With his newfound power, Brainiac/Luthor creates robotic clones of the Justice Lords and has them taunt the League with their insecurities; though Flash ignores his robotic-doppelganger's taunts and easily destroys it, and when his teammates finish of theirs, they are all knocked out when Brainiac/Luthor is fully complete and knocks everyone but himself out. Where he is gravely injured and captured by Nano-guards, and Brainiac/Luthor, thinking the Question was right, decides to kill him so that everyone else will go crazy and cause a war between all mutants & humans.
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The Flash pushing his limits in his super speed during his battle with Brainiac/Luthor.
But before he could do it, Flash breaks away and runs around the world to strike the fusion villain in the back, and after repeated runarounds, the Scarlet speedster taps into the Speed Force and is able to completely & permanently defuse the villain, as well as allowed to prove that no matter how much he wants to do it, Superman is no Justice Lord.
Afterwards, Flash and everyone else here an announcement from Superman saying that believing they've alienated from the world, decides to disband the League, but Green Arrow is able to change his mind and with everyone support, Superman decides to keep the League around and adds brand new changes to how they operate.
Flash Appreciation Day[]
The Flash rescues Linda from the mirror dimension in Flash and Substance.
After sometime, Flash heads to the Watchtower to tell everyone big news, but he only finds Batman and a visiting Orion while everyone else is of going on their respective missions. Flash tells the two that his hometown, Central city, is opening a museum in his honor. However, several members of his rogues gallery attempt to kill him to the point where he ends up being trapped in a mirror dimension with a reporter infatuated in him named Linda Park, but thanks to Batman, they are able to escape, and arrests them all.
Though during the scuffle, the museum was destroyed, but Flash didn't mind it. Afterwards, Orion begins to see the Flash in a new light, to which the latter remarks that despite everything that happened, he says it was a good day, stating that what matters most to him is that no one was hurt and the good guys won in the end.
Doing a "Freaky Friday" with Lex[]
During that time however, Flash along with the rest of the League found themselves at a war with another organization called The Secret Society, which is (unlike Flash's team) an organization of supervillains led by his enemy the hyper-intelligent Gorilla Grodd, which Lex has recently joined.
One day at the watchtower, while spending time with the sorcerer Doctor Fate, Flash get into a mishap where he gets his mind swapped with Lex's, after a crazy runaround in the body of Lex, Doctor Fate, with the help of Mister Terrific and Ice, they are able to get Flash in his own body and is able to learn where the Society's base is.
Battling Darkseid's Empire[]
While spending a normal day at the newly-established Metro Tower base for the Justice League, Flash and everyone else is shocked to find out that the Secret Society, now led by Lex (who shot Grodd into Space) had accidentally resurrected the literal God Emperor of Apokalips Darkseid, as he originally intended to resurrect Brainiac, and is now hellbent on conquering both Earth & New-Genesis, resulting in both sides to make a reluctant alliance to stop him.
Flash is transported to Paris to fight the invaders with Green Lantern and Giganta, after a long battle, The League wins when Darkseid and Lex are transported and become one with the Source Wall, in the aftermath, The League give chase to the remainder of the Society, but not before Giganta gives flash a surprise kiss.