Penguins

The penguins make their first appearance in the original short "Adventure Time," where Finn (known as Pen in the original short) and Jake use them as snow boards. Penguins live in the Ice Kingdom and seem to like the Ice King, Finn, and Jake as they were seen tickling Ice King and riding on Jake in "Prisoners of Love." They are friendly creatures. However, some of the penguins work for the Ice King. In general, they don't seem to have many concerns or motivation, they will do what Ice King asks but are easily distracted.

Penguins appear in the episode "Prisoners of Love," as well as in the opening scene of every episode that plays during the Theme Song. Many penguins have their souls sucked by Hunson Abadeer in "It Came from the Nightosphere."

As of "Princess Monster Wife," it has been revealed that there are many distinct penguins which all have names pronounced similarly to "Gunter" (such as "Goonter," "Gunther," "Günter," and "Goonther").

During Finn's dream in the episode "King Worm," penguins form the Ice Penguin Monsters who chase after the Ice King.

They drink the Ice King's tears as seen in "Five More Short Graybles".

Appearance
They all have eyes that look similar to Jake's. Unlike real penguins, they have a head the same size as their body.

Notable penguins

 * Gunter
 * Flower Girl Penguin
 * Guard Penguins

Trivia

 * Ice King doesn't seem to care much about most of the penguins he keeps in his company, as he throws several in the garbage after they bathe him in "Five Short Graybles."
 * In "The Chamber of Frozen Blades" it is shown that some of Ice King's penguins are female (despite his naming them all a variant of Gunter) as one gave birth. The Ice King seems to be unsure of Gunter's gender.
 * The concept of riding penguins may have been inspired by the pilot of Avatar: The Last Airbender.