Here are some ideas of Daniel from Voltron Force, what if in a forbidden kingdom a King and Queen who are the monarchs have Haggarium in their blood, and want to find someone who is infected with it to make that person into their child. They sent their servants to find a child or a teenager who is Infected with haggarium, one of them uses an orb that finds the location of the person and shows what he/she looked like. The orb shows a teen ( it Daniel Just to let you know ) the servant watches him fighting a tree that seems to have haggarium in it, then he noticed his eyes were Glowing purple like haggarium, the servant immediately reported it to the king and queen. When the servant was finished telling them what he/she saw in the orb, the couple look at each another and have decided to have Daniel here and look at his memories and study him before making the decision to make him into their child. They have ordered a doctor and scientist to make a cocoon that will make a person forget everything and another one that will make someone get used to Haggarium their system, as they started to work on that the king ordered three of his best spies to bring Daniel here. When they come back with Daniel who is fast asleep, the king and queen look at him and smile at each other then put him on a bed why someone looks at his memories along with the king and queen. When that was finished they woke him up, Daniel was panicking when he found himself with strangers in a room that was not his, he tried to get his weapon but couldn't so he got into a fighting state and his eyes were glowing. They quickly got something and used it on him and he calmed down but couldn't move much. He demanded to know where  he was, the servant explained everything to him and told him what they were going to do to him, Daniel tried to escape but couldn't, the king picked him up and he along with his wife and servant went to the cocoon that will be brainwashing him. The servants placed him in the cocoon with a breathing mask on, after two or three weeks it was finished, when they opened the cocoon Daniel was unconscious and was carried into a room where he was checked and cleaned up as they put fresh clothes on him, he slowly started to wake up. The doctor laid him down. But not before giving him something so his haggarium will be calm. Daniel asked lots of questions and one of them was who was he ? The doctor explains or lies to him about what has happened to him, then the King and Queen came in went over and hugged him they told him that they were his parents.

I will let you decide the rest. Will his friends and the Voltron Force save him before it's too late?

Here is another Voltron Force idea

What if Lotor's servants told him about Daniel ? That his eyes were glowing Haggarium and was aggressive why fighting, Lotor thought about this information when he suddenly got a message from Wade/Kala who explain how he and Kala infected Daniel with Haggarium. Lotor listens and slowly forms a plan, he orders Maahox to build a machine that will erase or brainwash someone and find something that will turn a person into an adult. Maahox nodded then went to build it, Lotor looked at Wade/Kale and called some of his best soldiers to help captor Daniel, they nodded and went along with Wade/Kala. Soon they come back with the struggle teen, Lotor walks over to him and studies him for a minute he then notices his eyes glow for a minute, he smiles at him and says this to him, you will make a fine edition to my army when we are done with you he said this to him. Before Daniel could say anything the guards put him in a room and were ordered to only give him food and water, it took two weeks for Maahox to finish the Machine and he found a place that will age someone into an adult. he took some samples of the waters and made a copy of it, Lotor ordered his guards to bring Daniel and have him put on a T-shirt and shorts. They forcefully push him in the water and after three minutes they pull him out of the water, Daniel is now a 21 year old man, he was then placed in the machine for his brainwashing process. When it was finished they put him in a nicer room and when he woke up. Lotor and Wade/Kala was there to greet him and explain who he was and what has happened to him.

Will they save Daniel and return him to normal ?

Here is a Keith idea from Voltron Legendary defender

What if Zarkon or Haggar somehow find out that Keith was Half Galra, Haggar asks permission from Zarkon to capture him and do some experiments on him. Zarkon approves of this and orders the capture of the red Paladin, when they got back with the unconscious Paladin. Haggar has been working on something that will change someone or something back into a child again, what if someone from the Blade of Marmora and Krolia volunteers to go and save him. What if the Paladin and Allura run into Krolia before anyone can do anything she explains who she is and her mission, Allura was about to say something when they heard a scream and a flash Shiro recognized it as Keith, they all ran to the room where they heard Keith scream. When they got there Haggar was there with 2 or 3 guards who were holding a child that Krolia and Shiro recognise as Keith, when they got keith back he didn't remember anything or anyone. Will the Paladin find a way to turn him back to normal ? How will they feel when they learn about Keith being half Galra.

Another keith idea

What if Zarkon wanted the red paladin for Haggar to study him, after a fight with him and one of the other Paladin who was with Keith at the time. (You can choose who is with Keith in the fight) when they capture Keith who is restrained and was struggling to break free. Zarkon was staring and studying him for a minute or two, then said you seem to act like a galra. Keith was staring at him in confusion, then Zarkon ordered Haggar to take a blood sample and other tests on him, then were taken away. After some time has passed Haggar reports were shocking to both herself and Zarkon, it was that they both discovered the red paladin was half galra.

I'll let you choose the rest.