Gluggagaegir is one of the Yule Lads. He appears in the animated series in "Chapter 10: The Yule Lads", and in the tie-in novel "Hilda and the Time Worm", but has a larger role in the latter. He does not appear in the graphic novels.
Gluggagaegir has a beard. He wears a costume like that of the other Yule Lads, but it is unknown in what color since he is not identified by name in the animated series, and the only image of him in the novelization is in black and white.
Gluggagaegir was once a human boy, who was targeted by Gryla for being naughty, in his case stealing food. Like 12 other children, Gluggagaegir 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.
In the animated series, Gluggagaegir is never identified by name and only appears in group shots of the Yule Lads. He and his fellow Yule Lads abduct Trevor, Trevor's mom and Johanna to feed them to Gryla. 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, Gluggagaegir and the other lads leave Trolberg.
In the novelization, Gluggagaegir sneaks into Hilda's room on the night of the Big Glow (when the Sonstansil blooms) in an attempt to steal Hilda's cucumber sandwhich. Hilda, who has been grounded by Johanna for her part in sabotaging the mechanical bellringers, catches him in the act. Hilda gives him her sandwhich on the condition that he never peeps through anyones window again. When Gluggagaegir questions Hilda about why she is grounded, Hilda tells him it's because of her mom being naughty; had Hilda not stopped the bells, Erik Ahlberg would have accidentally started a war with the trolls, thus Johanna is basically punishing Hilda for doing something good. Gluggagaegir is surprised to hear that adults can be naughty, and runs off to tell this to his fellow Yule Lads. Like in the animated series, they then proceed to abduct Johanna, but spare her when Hilda convinces them to give Gryla the broth instead.
- His name is Icelandic for Window-Peeper. In Icelandic folklore, Gluggagaegir was infamous for being a snoop who looks through windows in search of things to steal.