Gunter

Gunter (or Gunther) is the name Ice King gives to whatever penguin servant is closest in proximity to him. Gunter's gender varies since the penguins Ice King is around could be either male or female. Gunter has been confirmed to be a variety of penguins by Natasha Allegri and Andy Ristaino.

In "What is Life?," one of Gunter's known duties is being used as a stand for the Ice King's video game machine. Gunter also tried to warn the Ice King that Finn and Neptr were in the room. Gunter may be one of the penguins seen in the Theme Song in the Ice Kingdom. Gunter is mentioned in "What Have You Done?" when Ice King says, "Gunter, dispose of Finn's carcass." Gunter appears again in "It Came from the Nightosphere," where his/her soul is almost stolen and is dubbed "the most evil thing in the world" by Marceline's Dad. Gunter appears in "The Chamber of Frozen Blades" and is very sick, but it later turns out she was pregnant and the egg hatches revealing a floating pink kitten. Gunter may also have appeared in other episodes featuring penguins, although it's impossible to tell because Gunter is indistinguishable from other penguins.

Gunter re-appears in the episode "Still" trying to mess with the potions Ice King brought to freeze Finn and Jake. Ice King says that Gunter likes to break bottles. He/she is shown to be a troublemaker in this episode.

A number of Gunters appear in "Holly Jolly Secrets Part I" and "Holly Jolly Secrets Part II." Notably, during his "Penguin Dance Party" video, Ice King calls two different penguins "Gunter" in the same scene. This is the main in-show indication that Gunter is not a specific penguin.

In "Five Short Graybles," Ice King makes Gunter float out to sea on an iceberg because he believes that Gunter is making his cave smell bad. It also shows that Gunter can play the keyboard, though not very well.

In "Princess Monster Wife," only one penguin is called Gunter and many other penguins are addressed with similar, though different, names.

Appearance
Gunter looks like a regular penguin with big black eyes, a black back and a white flat belly.

Relationships
The Ice King sometimes gets upset at Gunter, such as when he/she accidentally broke his video game or ate his socks, but the Ice King seems to appreciate his/her company. The Ice King often speaks to them like a father.

In the episode "Five Short Graybles", The Ice King was able to distinguish one penguin from all the others. The episode "Princess Monster Wife" confirms that the Ice King indeed does know all of the penguins by name and all are named some variant of Gunter (e.g. Gundy, Gunder, Gunthy, Goonter, Günder (Gewn-der)...).

Trivia

 * Gunter's page on the Cartoon Network website explain a lot: 'Gunter is the name the Ice King gives to all of his penguin servants, yet he pronounces it differently depending on the penguin's personality.
 * Princess Monster Wife revealed that the penguins are not all named Gunter. They have variated names like "Gunther", "Goonter", "Gunder", etc.
 * Gunter, for some reason, was dubbed the most evil creature that Marceline's Dad had ever seen, indicating that one of Ice King's penguins may secretly be evil and smarter than others realize.
 * Although Gunter is a penguin, he/she makes a "wenk" sound.
 * The father of the pink kitten that comes out of the egg Gunter nurtures is unknown.
 * In "What is Life?," the Ice King comments on Gunter gaining weight. This may foreshadow Gunter's pregnancy, though it could be that particular penguin was fatter than the last one he called Gunter.
 * Although the name is spelled "Gunter," it's been pronounced "Gunter," "Gunther," and "Goon-ter".
 * Gunter (variations: Günther, Gunthar) is an old German name made of the words Gund ("Fight", "Battle", "War") and Heri ("Crowd", "Folk") referencing the fact that Ice King calls all his penguins Gunter making them his army.
 * For some reason, Marceline's diary had the name Gunter on it in the episode "Marceline's Closet."
 * In the episode Holly Jolly Secrets Part I it's revealed that any penguin closest to Ice King is "Gunter."
 * It seems that Gunter often goes into Ice King's arms as revealed in Five Short Graybles, and stinks up Ice King's armpits.