Ketkrokur is dressed in a yellow costume, but a different shade than Pvorusleikir. He has a thick beard.
Ketkrokur was once a human boy, who was targeted by Gryla for being naughty. It is not stated in the series what exactly he did, but when he interrogates Hilda, Frida and David, he asks them if they ever threw rocks and/or heavy sticks at their neighbors window. Since Stekkjarsaur also questioned the three kids about something that he himself did, it can be assumed that the rocks/sticks throwing was Ketkrokur's crime.
Like 12 other children, Ketkrokur made a bargain with Gryla to find her more naughty children in return for being spared. Now, every year around the Trolberg Winter Festival, he and his fellow Yule Lads come to Trolberg to find and abduct naughty children.
When first seen "Chapter 10: The Yule Lads", he and his fellow Yule Lads have just arrived in Trolberg, and are found by Hilda, David and Frida. He is mostly a background character during the episode. When Hilda finds out what they are doing, she suggests the Lads to give Gryla the Sparrow Scouts' vegetable broth as a substitue. Gryla accepts the broth, and after she is gone, Ketkrokur and the other lads leave Trolberg.
- In Icelandic folklore, which the character is based on, Ketkrokur was said to use a hook to steal meat.
- In "Hilda and the Time Worm", his name is translated as "Meat Stealer", which corresponds with the Icelandic Folklore.