"Unleashed" is the fifty-first episode of the first season of Justice League Action. It is the overall fifty-first episode of the series. It features the first apperance of Streaky the Supercat.
While the Justice League is away on a mission, Plastic Man is not only left in charge of the Watchtower, but also Superman's dog, Krypto.
The Justice League is preparing to mobilize through a Boom Tube to protect Earth from an oncoming invasion by the Red Lantern Corps, with Batman, Superman, Supergirl preparing to head out. Plastic Man wants to come along too, but Superman has a better idea and wants him to stay behind for an important job. At first Plastic Man is excited as this means he will be in charge of the Watchtower, but Supergirl says that isn't what they had in mind and the auto defenses are now active to protect the Watchtower, with Batman noting that the computer outranks Plastic Man. It turns out that the job is to dogsit Krypto, whom Plastic Man reluctantly takes for a walk to do his business. Plas tries to clean up after Krypto, but the super canine takes care of that for him with his heat vision. Krypto tries to cheer Plastic Man up by licking his face, only for Plas to hear the meow of a cat. The two of them see a blue cat in the water floating on some driftwood and Plastic Man saves it.
He takes the cat inside the Watchtower and dries it off, not sure how he was able to turn his hands into blow driers. The cats shakes off its fur and gives Plastic Man a cute face, with the superhero wondering if the cat is hungry. As soon as Plastic Man goes down the elevator to the kitchen, the cat jumps off the table and presses the button for the other elevator. Krypto wakes up from his nap and sees this, immediately becoming suspicious of the mysterious cat. The cat enters another level of the Watchtower and presses a button on his collar, revealing he is actually Dex-Starr, a Red Lantern lieutenant of Atrocitus, Leader of the Red Lantern Corps! Atrocitus congratulates his most trusted soldier for infiltrating the Watchtower and gives Dex-Starr instructions to not use his Red Lantern Power Ring and maintain his cover. Dex-Starr deactivates the base's anti-teleportation defenses and sends a signal so a small squad of Red Lanterns will come through and begin the invasion while the Justice League is distracted.
Krypto overhears Dex-Starr talking to Atrocitus and attacks, but Plastic Man stops them both and thinks Krypto messed with the control panel. He carries Dex-Starr away to the kitchen while Krypto has to stay in the control room.
Plastic Man is reading books on how to care for cats and offers Dex-Starr some sushi. The cat humors him and eats it, smiling, but also trying to slip back into the control room to finish his task. Plastic Man thinks Dex-Starr is still hungry and feeds him more food, restraining the cat every time he tries to leap off the table. After several courses, Dex-Starr is too stuffed to even move and has a stomachache, yet Plastic Man offers him dessert and want to bake Dex-Star an entire cake (made with Asparagus). Dex-Starr is fed up with Plastic Man's attempts to stuff him and tries to get away, only for Krypto to be right near the counter. Dex-Starr quickly comes up with a plan to remove him from the kitchen by framing him for knocking over his dessert. Krypto tries to catch the dessert, but Dex-Starr uses his tail to knock it over and break the plate to get Plastic Man's attention. Once again, Plastic Man thinks Krypto is the culprit and gets mad at him, carrying Dex-Starr to another part of the Watchtower to watch TV.
Dex-Starr is sick from all the foods he ate and needs to use the litter box. Before he can make it there, Plastic Man picks up Dex-Starr and thinks the cat is still hungry because of his growling stomach. Dex-Starr is left alone as Plastic Man goes to the kitchen to make more meals for his new pet. As he tries to make it to the litterbox, Atrocitus contacts him and is impatiently waiting for Dex-Starr to deactivate the Watchtower defenses and turn on the signal. Dex-Starr reluctantly holds it in and goes towards the control panel, only for Krypto to emerge from behind it and chase him, firing short bursts of heat vision at him to keep Dex-Starr away from the panel.
Meanwhile, Plastic Man is in the kitchen making a cat smoothie with sardines and flower petals when he hears the two pets fighting and sees the control room is on fire. He yells for them to stop and Dex-Starr pretends to be hurt so Krypto can take the blame again. Outraged at what the Dog of Steel has done, Plastic Man throws him into a sun room and turns on the red solar lamp to remove Krypto's powers as punishment until Superman gets back for being a "bad dog". Plastic Man carries Dex-Starr back to the control room and prepares to give him his cake. Not wanting to put up with anymore of Plastic Man's "love", Dex-Starr throws the cake in Plastic Man's eyes and breaks his cover by donning his Red Lantern Ring to attack him. The Watchtower blares an alarm as the computer shows Dex-Starr's data file to Plastic Man. Hopelessly outmatched, Plastic Man cries for help while Krypto struggles to break down the door to the sun room. Realizing he can't break it down without his powers in time to save Plastic Man, Krypto grabs the dog tag on his collar and bites down on it to send out an ultrasonic high-frequency distress signal that only Kryptonians or Kryptonian-like beings can hear.
The signal goes out to Metropolis, where Supergirl's cat Streaky is saving a couple from a man with a dog attempting to rob the couple at gunpoint by tying the man and the dog up with the dog's leash. Streaky hears Krypto's SOS, picks the mugger up and drops him in a garbage truck and swiftly heads to the Watchtower.
Back at the Watchtower, Dex-Star hits Plastic Man with a fly swatter construct and then melts him with a heat-enhanced Red Lantern energy hairball. Dex-Starr then prepares to tamper with the Mother Box in the control panel to finish his task, but soon sees Streaky hovering over him with a heroic but smug look on his face. The two superpowered felines immediately clash and eventually bring their fight to the floor Krypto's sun room is in. Krypto barks for his old pal Streaky to free him, but Dex-Starr blocks Streaky's effort with his Power Ring and then slams the heroic cat with another construct. The feline Red Lantern's rage gets the better of him however as Dex-Starr uses a construct of a subway train to run Streaky over and unintentionally breaks the sun room door open and busts a hole in the wall. Krypto is free and slowly getting his powers back now that the morning sun is coming up. Realizing he messed up big time, Dex-Star brings the roof down on the two Super Pets to buy him some time to get to the control room. Krypto shakes it off, but it is too late as Dex-Starr has activated the beacon.
Dex-Starr once again tries to get to the litterbox, but is stopped by Krypto. Soon Streaky arrives and tag teams with Krypto and the two try to take on the Red Lantern, but an alarm goes off as an unauthorized Boom Tube has emerged outside and an army of Red Lanterns are starting to come through. The two Super Pets decide to split up, with Streaky fending off the Red Lanterns while Krypto tries to deal with Dex-Starr. Krypto does his best, but is still a little weak from the red sun exposure and is then trapped in a bubble construct. Streaky fights valiantly against the Red Lanterns and manages to hold his ground until all the Red Lanterns focus their rings on him in a concentrated burst and blast him away. Dex-Starr at first revels in his victory, but then really really need to go to the litterbox. Once inside, his Power Ring is taken off his tail and it is revealed that Plastic Man recovered, moved the actual litterbox and shape shifted into it to spring a trap for Dex-Starr. The bubble that had imprisoned Krypto fades away and Krypto shuts off the Mother Box to close the Boom Tube and put the Red Lanterns back on their side of the universe.
When the League returns, Plastic Man explains what happened to Superman, Batman and Supergirl while still holding onto Dex-Starr inside his body by taking the form of a burlap sack and being held by the neck by Batman. Superman realizes that the plan of the Red Lanterns all along was to execute a diversion to take out the Watchtower and pets Krypto for being such a good boy in protecting the Watchtower. Batman is unsurprised that the Red Lanterns sent a cat as an agent to do the deed. Supergirl says that cats are full of surprises as she holds a tired Streaky in her arms. Plastic Man admits he only helped and Krypto and Streaky were the real heroes of the day when Superman gives credit to him. Plas then ends the episode with a terrible poop joke while coughing up cat litter.