They are a kid who helps Frisk throughout The Chilly Mines. They are very determined to become a royal guard and is getting training from Papyrus until they are old enough to be a guard. they are very strong for their age due to intense training. At first they were portrayed as a boy but because there will be a Next Generation for the AU featuring a Frisk x Monster Kid ship child they were changed to be genderless because of how Frisk is either gender They can be a boy or a girl for depending on your headcanon. People call them MK as they hate their real name. Like in the original they look up to Undyne.
They are confident, energetic, and hot headed. They strive to make the Underground a better place when they become a guard. They think of Papyrus as their cool older brother. When they have a hard time making important decisions they ask Sans for help. They can get flustered easily so they would be the perfect flirting target for any AU Frisk.
Soon to be added