The Yule Lads each have a different naughty hobby. There's Spoon-Licker, who steals wooden spoons. Door-Slammer, who slams doors in the middle of the night. Sausage-Swiper, who sneaks into kitchens to take sausages. Window-Peeper, who peeks through windows. Each one is silly rather than scary - they're famous troublemakers, but they are kind underneath.
Icelandic children put one of their shoes on the windowsill each night for 13 nights. If they have been good that day, the visiting Yule Lad pops a small treat or toy into the shoe. If they have been a bit cheeky, they might find a potato instead. (Many Icelandic children have, at least once, woken up to find a potato.)
The first Yule Lad arrives on the night of 12 December. The thirteenth and last one arrives on Christmas Eve, 24 December. Then, starting on Christmas Day, they leave again one by one, until the very last one heads back to the mountains on 6 January - thirteen days after Christmas.
All thirteen are the sons of two huge, gentle, grumpy mountain trolls called Gr媒la and her husband Leppal煤冒i. They have a big cat too - the famous Yule Cat - which prowls the snow at Christmas. It only bothers children who haven't received any new clothes that year, so Icelandic families are extra careful to give each other something warm and new for Christmas.