Shendak

Shendak is the Slash ship between Takashi Shirogane and Sendak from Voltron: Legendary Defender

Canon(?)
Since user Our Green Tornado is addicted to Shendak, she made a petition for it to gain canon status(and for Zarkon to prevail). She even made a fan movie inspired by Moulin Rouge(Operation Shendak) for it, and chose a love anthem(Ain't No Mountain High Enough by Diana Ross) for it.

Yoshida Zarkon
Yoshida Zarkon is a title given to Zarkon shipping Shendak, first intrduced in Operation Shendak.

Operation Shendak
The movie kicks off in the Galra Empire("Overture"). Shiro, the Champion of the Galra, is shown with his favorite commander, Sendak. The systems play their love theme as they dance around an empty hall("Come What May"). A year later, Shiro, now the Black Paladin of Voltron, has completely forgotten about Sendak. He falls in love with Princess Allura of Altea, as his friends Keith, Lance, Hunk and Pidge cheer him on, and Keith develops a crush on Allura("Assembly"). Meanwhile, in the outside world, Movie Director Jae Oh(user Our Green Tornado) phases into the Voltron universe in attempt to reunite Sendak and Shiro("Eye Of The Tiger"), but before she can get to Sendak, the Arusian king spots her and she flees outside. Later, she re-enters the Voltron universe with big plans-teaching Emperor Zarkon to make him a hero and use him as a "Yoshida" for Sendak and Shiro, just like Yoshida Ultron did with Iron Man and Captain America. She gathers some sentries and instructs them to build an education center in Galaris that looks like the top floor of a 99-storey skyscraper. She then returns to the Castle Of Lions and join the Paladins in their training("Mighty Roar").

Later, the Director goes to Galaris to see Zarkon and leads him to the education center. She teaches him many things through videos, photos, and holographic images("Colors Of The Wind"). She then tells him that "she won't stop 'till he's his Black Paladin-y self all over again" and leaves, leaving a really confused Zarkon behind. The Director returns to the Castle Of Lions, and Allura offers her to stay for the night. The team and Arusians celebrate together in the castle, but the festivities come to a halt when Pidge reveals her intentions to leave the team and search for her missing father and brother. As the team tries to convince Pidge to stay, Haxus, one of Sendak's soldiers, is able to sneak a bomb drone into the castle, causing it to destroy the crystal that powers the entire castle and severely injure Lance in the process. Coran and Hunk leave to acquire a new crystal, Keith and Allura rush to the Arusian village as it is being attacked by the Galra while Shiro and Pidge remain at the castle with Lance. However, Sendak attacks and overpowers Shiro before plugging a Galran crystal into the castle, the attack on the Arusian village being a distraction. Pidge evades capture and with Allura's guidance is able to sabotage the Galra's efforts to launch the Castle. Meanwhile, Hunk and Coran arrive at a nearby Balmera, a large petrified creature the size of a planet from which the Alteans acquire crystals. They discover that it has been taken over by the Galra and crash in the subterranean mines.

The two meet local Balmerans, Shay and Rax, who help them hide from the Galra. Shay admires the two and wants to help them, but Rax is cautious and insists they leave. Hunk and Coran are able to sneak past the Galra to find a crystal, but are captured and imprisoned. Shay helps them escape with the crystal, but is captured by the Galra after her brother informs them of Shay's actions. Hunk promises to return and save her people before he and Coran return to Arus. Still trapped outside the castle, Keith and Allura are unable to help Pidge take back the Castle. With Allura's guidance, Pidge is able to continuously sabotage the Castle's systems to further delay Sendak's take off. In flashback, Katie Holt watches the news in horror as she learns of her father and brother's apparent demise on the mission to Kerberos. Katie breaks into the Galaxy Garrison and accesses Commander Iverson's files of the mission. When she is caught by Iverson, she presses him about the crash despite probes showing no evidence one but Iverson reprimands her and bans her from ever entering the Garrison again. Some time later, Katie enrolls in the Garrison, but cuts her hair and wears glasses, passing herself off as a male student named Pidge Gunderson.

As the flashback ends, the Director discovers Pidge driving Haxus to death. When Pidge threatens to kill Sendak, the Director punches her in the face, telling her that "this is her job". The space mice are able to take down the particle barrier, allowing Allura and Keith to enter the Castle and help Pidge against Sendak. After the hubbub settles, Pidge writes an epic novel called "Shiro, The Champion Of The Universe", criticizing the Director and her matchmaking plans through the book. The Director reads it and compliments Pidge instead of being mad at her, telling that "it would have been a smash hit if it was published on Earth". Feeling sorry for the Director, Pidge tells her that she will never interfere in her plans ever again, before revealing her gender to the rest of the group. Later, the Director goes to Galaris and tells everybody that she will host a play called "Celeste Zarkon(Heavenly Zarkon)", to let the universe know about Zarkon's change, and the gladiator arena is converted to a theater("Love Withot Tragedy"). As the Director continues on her lessons, Zarkon begins to grow fond of her and they eventually grow closer together("Friends"). One day, during a lesson, the Director keeps telling Zarkon to model Spider-Man. Zarkon gets mad and tells her that he's not Spider-Man, and they argue. Haggar arrives, seizing the Director with her dark magic and putting her in prison, and the education center is closed off.

As days pass, Zarkon and the Director are increasingly lonely and miss each other("Shattered"). Zarkon continues to teach himself and begins to draw out the greatest and most powerful matchmaking plan ever, to impress her("Under Pressure"). Meanwhile, the Director begins to sing in her cell("Hello"), hoping that somebody will come and save her. A Galran lieutenant named Thace hears the song, and rescues her. She tells him that she has to apologize to Zarkon, amd goes to the command room unprotected. Haggar once again attempts to harm her, but Zarkon throws himself in front of her, blocking the attack. The Director tells Zarkon that he is a good man, and asks him if he will be "Yoshida Zarkon". He says he will, and takes her out to show her his plan. She is impressed, and Zarkon tells her that he will do his best to follow in Spidey's footsteps and become a "friendly neighbor" just like him. ("The Children Of The Revolution(Avengers Medley)")

Later, the Director brings Zarkon into the Castle Of Lions, much to Allura's dismay. They and the Paladins pitch "Celeste Zarkon" to Allura with an improvised plot about an evil, rich woman attempting to woo a handsome astronaut who loves a Galra general("The Pitch"). Allura backs the show on the condition that only she may see Shiro. The next day, Zarkon and the Director brings Thace into the Castle to stay, and Keith realizes that Thace is his father. Sendak and Shiro continue seeing each other under the pretense of rehearsing their lines. Allura becomes suspicious of their frequent meetings and tells Pidge and Coran to keep an eye on the two. Back on Galaris, Zarkon calls his ultimate weapon Arusian Jerry, who loves Keith. Jerry tells Zarkon that he will never let him down. After Jerry leaves, the Director arrives and accuses Zarkon for still being evil. On their way to the Castle Of Lions, the two spots a small kid being bullied by larger kids. Zarkon vanquishes the bullies with his skills, and the kid is mesmerized. He asks him who he is, ans Zarkon tells him that "he's just an apprentice superhero who used to be The Conqueror Of The Universe". He and the Director bids goodbye to the kid, and heads on their way back.

When they arrive, Voltron is defeated. Jerry tells Keith that he will stop this madness if he marries him, but Keith says he can't, stating that "his heart belongs to somebody else". Lance and Shiro expect that somebody to be one of them, but instead, Keith reveals his crush on Allura, telling everybody that he's heterosexual. Jerry tells Keith that snails can change their biological gender at will, and turns into a woman, changing his/her name to Jerrika. Keith falls for her immediately, and they get married in the Castle, with Haggar as their officiator. The Director sings two special songs to celebrate Keith and Jerrika's marriage("Get Loki", "Ultron Funk"). Suddenly, a space blizzard hits the Castle, and everybody except Zarkon and the Director panics. Jerrika begins to scream, but Zarkon silences her with a blow from his bayard sword, just like he did to a young Allura 10000 years ago, and the gang heads to the Balmera to save it. On the way to the Balmera, the gang stops to help two rebels, Rolo and Nyma, on the run from the Galra. While the others are open and trusting to the pair, Hunk is cautious and guarded and eager to get to Balmera as soon as possible. Lance flirts with Nyma, and the Director introduces Zarkon to the pair. After having a good time, the gang continues on their way, leaving Rolo and Nyma behind.

Allura, Coran and the Paladins return to the Balmera to free the natives, but must hold back their firepower so as not to hurt the Balmera. Shiro and Pidge scout for Galran forces, who are strangely absent, while Lance and Keith work to disable a Galran fleet of ships. Hunk searches for the prisons and is able to find Shay's family, including her brother Rax, but learns that she was taken by the Galra to the heart of the Balmera after they arrived. The Paladins make their way to the Balmera's core to rescue her, but fall into a trap. Shay uses the Balmera to transmit a message to her family, who are able to free them with the Balmera's help. The Paladins form Voltron and are able destroy the Galran fleet, but their victory is short-lived by the invasion of the Crystal Raiders. Allura decides to perform an ancient ritual once performed by her people to rejuvenate the Balmera, while Rax is cornered in a corner by the Raiders. Zarkon rescues him and reunites him with his family, proving to the Balmerans that he has changed. Allura's ritual is able to revive the Balmera, and Zarkon is on Weekly Volcano, a really famous space newspaper for saving Rax.

The gang then returns to Earth to recruit human actors for "Celeste Zarkon", and meets Colleen Holt, Pidge's mother who befriends Zarkon. Suddenly, the Director receives a distress signal from Sam and Matt Holt, and gathers everybody to go save them. Just outside the Earth's atmosphere, the gang finds Sam and Matt's transport capsule surrounded by amoeba-like predatory extraterrestrials called Vermicious Knids. The Knids dive-bomb the capsule, destroying the rockets, cameras, and radio antenna, apparently stranding the occupants in space. Zarkon and the Director pilots the Castle into range, whereupon Coran connects the two vessels with a steel cord. The Knids change into living segments of a towing line, with which to capture the two spacecraft, while a single Knid wraps his body around the Castle to provide an anchor for this operation; whereupon Zarkon returns the Castle to Earth, and the Knids are incinerated in the atmosphere. Allura is infuriated by the Director calling Zarkon "a hero", and attempts to kill him in a forest back on Earth. Zarkon retaliates by shaping the Black Bayard into a shield, knocking her down. He then reunites with the rest of the gang and the Holts, where Zarkon’s tragic and austere exterior is cracked for good as the Director tells him that she loves him.

The gang returns to space with a group of Garrison astronauts who decided to participate in the play, and as Allura watches Sendak rehearsing with Shiro, Prorok, a jealous Commander, points out that the play is a metaphor for Sendak, Shiro and Allura. Enraged, Allura demands the ending be changed with the astronaut choosing the rich woman; the Director comforts her, tells that Shiro loves her, and sings her a song to keep the original ending("One Night Only"). She then imagines Sendak and Shiro together once more("Deep End") as Allura tells her that she will have Sendak killed if Shiro is not hers. Annoyed by this, the Director prepares Operation Shendak, an invasion force of 75000 Galra troops and over 200 battle cruisers upon all non-Shendak shippers which she based on Zarkon's plan. She decides to send the wave to the outside world through an intergalactic bypass, and Zarkon cooperates in the operation("The Show Must Go On"). The plan works, and most non-Shendak shippers are eliminated.

The night of the the show, everybody is excited to see a matchmaking masterpiece, although Shiro is still reluctant to work with Sendak. Suddenly they find themselves in the spotlight; Zarkon improvises and convinces the audience that Sendak is the general in disguise. With the aid of Zarkon, Sendak and Shiro safely reconcile on the gladiator arena. Allura proposes to Shiro, but now that he has Sendak, he says no. From the other side, Thace cries out, "The greatest thing you'll ever learn is just to love and be loved in return", spurring Sendak to sing his and Shiro's love theme. Shiro returns to the arena, joining him in the song and reaffirming his love for him. Allura orders Keith and Lance to kill Sendak but they refuse, while her own attempt is thwarted by Zarkon("Come What May(Reprise)", "Coup d'État(Finale)"). The spectators cheers, stating that "it is the best show they've ever seen".

Later, a ball is hosted in the Castle Of Lions to celebrate the success of Operation Shendak. Zarkon holds his hand out to the Director, and they dance together("Angel With A Shotgun").