These troll-like brothers, sons of the terrifying ogress GrĂ½la, visit Icelandic children over the 13 nights leading up to Christmas. Each Yule Lad has a quirky personality, like Spoon-Licker or Door-Slammer. Good kids wake up to sweets and small gifts in their shoes, while naughty ones find a rotten potato instead. The tradition keeps children entertained (and well-behaved) for two full weeks.