MK is a noodle delivery boy and the successor of the Monkey King. When MK learns that the Demon Bull King was freed from his imprisonment, he, along with Mei, Pigsy, Tang, and Sandy, went on a quest to give the Golden Staff back to the Monkey King, in hopes that he can defeat the Demon Bull King again. However, when MK went to the Flaming Mountains with Mei and Pigsy, he was presumably killed by Princess Iron Fan. But when MK realized that he ended up in Flower Fruit Mountain, he meets Monkey King and was inspired by him to believe in himself and take the Golden Staff back. When MK returned to the city, he reunites with friends and celebrated with them after defeating the Demon Bull King, earning the title Monkie Kid.
A week later, MK continued to battle demons as well as facing difficult challenges. Although, when the Demon Bull King freed Lady Bone Demon from her tomb, MK teams up with Princess Iron Fan and Red Son to free DBK from Lady Bone Demon's control and became successful.
When the Spider Queen and the Spider-Bots started taking control of the civilians at New Year's, MK wasn't sure what to do after Monkey King got captured by her. However, when Red Son says he can find an antidote that can cure the citizens, MK and the rest of his team teamed up with him to travel to the Celestial Realm to and retrive the Celestial Artifacts.
After Monkey King left to go on vacation, MK began to wonder if the Monkey King picked the wrong successor after learning Lady Bone Demon's identity. Eventually, MK learned that the Spider Queen was being used as a pawn for Lady Bone Demon and attempted to fight her, but lost his powers as a result. However, after MK realized that Monkey King lied about going on vacation and was actually looking for a weapon that could defeat Lady Bone Demon the whole time, he and the others joined him on a quest to look for it so they can beat the Lady Bone Demon.
MK is a typical teenage boy. He enjoys hanging out with his friends, playing video games, and is often easily distracted when it comes to his job. MK is a fanboy of the Monkey King, knowing almost everything about his background. Upon gaining the Monkey King's Golden Staff, MK seeks to become hero like the Monkey King. However, he tends lose focus on the task at hand, and can be impatient when to comes to his training. He has severe arachnophobia but can overcome it when his life is at stake.
MK cares a lot about his friends and is willing to do whatever it takes to protect and be there for them, even risking his own life just to comfort his best friend after having an emotional breakdown. MK is incredibly empathetic, accepting and encouraging the help of Red Son and Macaque, even though both were his enemies at the time.  He believes that you cannot judge something by its worst qualities and that there is perfection in imperfection.
Despite his kind heart, MK is still a bit of a jerk sometimes and hes got an ego.
Monkey King's absence and Lady Bone Demon's interference caused MK's insecurities to grow. He felt that the Monkey King had made a mistake and that he wasn't fit to be his successor. He hides these feelings and becomes distant from his friends in order to protect them. Hes frustrated with Monkey Kings departure in Season 2, though it manifests more as self-doubt than anything else.
MK has admitted that sometimes, he plays dumb to lighten the mood.
In LEGO Brawls (non-canon)
MK is a playable character in LEGO Brawls. He is the first character that can be unlocked after collecting enough Season Trophies in the first week of Season 14 of LEGO Brawls, A Hero is Born. In addition, MK's Hero variant can be unlocked in the final week of Season 14, Team Monkie Kid.
Weapons & Accessories
MK's book is a red book that contains the history of the Monkey King. The front cover depicts a drawing of MK and Monkey King.
MK occasionally uses his headphones to listen to music either while delivering noodles or on his free time.
MK's phone is a handheld object owned by him. He mainly uses it as a GPS whenever he delivers noodles. It has a noticeably cracked screen.
The Golden Staff
However, during his battle with the Lady Bone Demon, MK lost the Golden Staff after his powers were taken. He later gained it back before defeating the Lady Bone Demon.
During his entrapment in the Trigram Furnace, MK found himself hopeless until he saw his reflection, who told him that he was on his own and that he needed to figure a way out by himself. Even though he struggled at first, MK took his reflection's advice and was able to escape from the furnace.
When the Lady Bone Demon attempted to trick MK into striking the furnace with his staff, his reflection frantically warned him to stop, causing MK to catch onto her ruse.
It's worth noting that MK's reflection is presumably not another living being like his clones, but a representation of his inner thoughts and subconscious for the audiences benefit.
Due to him having the same powers as Monkey King's, MK can create multiple versions of himself by using strains of his hair. Although, MK can only keep the clones docile depending on how well he can control his powers. Otherwise they would overdo what they were told.
Note: Italicized text indicates all of MK's former abilities.
Via the Golden Staff
MK is an in-universe nickname, presumably a reference to his title as the Monkie Kid.
His name in the Chinese dubs, Qí Xiǎotiān (齐小天) translates to Together Little Sky. Xiǎo (小) meaning little and Tiān (天) meaning sky. The surname Qí (齐) is the simplified character for 齊. Both these characters come from Monkey King's title: "The Great Sage, Equal to Heaven" or Qítiān Dàshèng (齊天大聖).
Names in other languages
Behind the scenes