A Transplant for Blue Lion is the thirty-second episode of the lion series of Voltron: Defender of the Universe.
In Castle Doom, King Zarkon congratulates his son, Prince Lotor, on the recent raid on planet Arus, which crippled Voltron.  Zarkon mentions that Lotor should have pressed the advantage, but Lotor points out that without Blue lion, Voltron can not assemble. Lotor mentions intelligence reports that Blue Lion is still heavily damaged and may never fly again.
Meanwhile, in the Castle of Lions, Princess Allura walks down a hallway in the main keep, her right arm in a sling. Nanny asks why she is not resting, and the princess replies that Arus needs her. In the control room, Coran mentions that repair crews are working around the clock to get Blue Lion back in action. Keith says that Arus should test its defenses without Voltron. King Alfor appears on the main monitor. The dead king describes the lions as five streams flowing into a river. A river could carve a mountain and break down rock, but only if the streams are strong. Lance wonders why the king speaks like that. Keith understands and says they need to train to make themselves and the lions stronger. Keith gets ready to deploy, and Lance disrespectfully scoffs at the idea. Keith grabs Lance, and Allura tells him to knock it off. The Voltron Force all agree to start training. Coran points out that the people in the capital could be in danger if Lotor attacks. The Voltron Force head out in hovercraft to the city to warn the residents and have them relocate to the castle. Going to an empty street, they wonder where the people are. Then they see the people, all armed. One of them says they are ready to fight for Voltron and Arus. Lance says that their lasers will not be very effective, and the man says his unborn child is relying on him to defend their home. This show of bravery fills Allura's eyes with tears. Coran then informs them that the repairs to Blue Lion were completed. Keith and company return to the castle.
Back on planet Doom, Haggar's Robeast is finished. Lotor is excited at deploying the Robeast to crush Arus. The Robeast looks the same as the one that crippled Voltron not long ago. With her magic, Haggar upgrades it.
On Arus, the Voltron Force go on a drill in their lions. They dive towards the alpine lake where the Castle of Lions is located. The massive acceleration strains the pilots. The lions splash into the water. They then attack gun emplacement that were placed underwater. Blue Lion is hit and strikes the side of the castle's island. Keith insists that Allura figure out how to get out of it on her own. She manages to dodge the guns and flies out of the lake. Inside the control room, nanny asks Coran to stop, and Coran replies that the Voltron Force, including Allura, need to train harder than ever.
Keith announces that they will form Voltron and the castle will fire on them. The others are surprised. Voltron is formed, hovering near the castle. Coran gives the order to fire. The castle fires its lasers and missiles at the robot. Voltron uses countermeasures to take down the missiles. Keith then announces that they will practice evasive maneuvers. Voltron then evades the castle's fire. The left leg is suddenly hit, and Yellow Lion detaches from Voltron. Hunk takes control and reattaches Yellow Lion. Keith then asks the castle to target Hunk and they do. After dodging a few shots, the castle scores a direct hit and Yellow Lion detaches and crashes into the ground. Hunk is frustrated and in tears, thinking he let the team down.
The team later meets where Yellow Lion crashed. Hunk is ashamed of his failure. Keith tells him to pull together and that they will all continue training. But their training will be put to the test, for Lotor has come with an attack fleet. He attacks the capital, and two of the infantry actually shoot down fighters with their lasers. Lotor's ship fires a capsule and releases the Robeast.
Hunk asks Keith to lead the attack, and he does, firing rotor missiles. Yellow Lion doges the Robeast's fire, and gets hit. The Robeast hits the other four lions in a grip ray and they are thrown into the capital city. The people of the city provide cover fire for the lions. Keith orders a power dive, and the lions dive right into the Robeast's head, destroying it. The lions assemble into Voltron, and the Robeast aims at it with its chest cannons. It grows a new head and fires. Voltron is caught in some kind of beam. Keith orders an X-ray probe. Finding the main power source, he orders an attack. But Voltron can not hit the Robeast's power source. Suddenly, King Alfor appears again, telling the team to concentrate their strength.
Keith locks the power harness and orders a power buildup. Voltron powers up, and the lion heads detach and punch through the Robeast. After reattaching, Voltron forms the blazing sword and slices apart the Robeast. Lotor flees in his ship. Meanwhile, the Voltron Force sees a newborn baby, who was named Voltricia.
"Wow, King Alfor speaks like a corkscrew. Why can't he just come right out and say what he means?"
— Lance points out King Alfor's inspiring speech is a bit too cryptic to be inspiring
"Streams coming together to make a great strong river. People are like that, coming together, working together to make a strong family a strong city, a strong country, a strong planet. But the key words are working together. That's what makes a mighty river or a mighty Voltron."
— Keith's inspiring speech is a bit less cryptic than King Alfor's
Lance: "Hey, team, while we were busy, a new baby was born on Arus."
Hunk: "Cute little guy. I hope they name him Voltron."
Pidge: "It's not a little guy; it's a little girl."
Allura: "And they're naming her Voltricia!"
— Voltron receives the honor of having a baby named after it/him
Notes and Goofs
- In one scene Keith is animated wearing Lance's blue uniform.