The Icelandic actor was first diagnosed with pancreatic cancer in 2016. He shared details of his treatment on social media and at one point seemed to suggest he was recovering after surgery.
But in March this year he announced that the cancer had returned and was terminal. In a statement about his condition he said: “It’s not until they tell you you’re going to die soon that you realise how short life is.
“Time is the most valuable thing in life because it never comes back.
“And whether you spend it in the arms of a loved one or alone in a prison-cell, life is what you make of it. Dream big.”
The actor’s wife Steinunn Olina Porsteinsdottir, posted an emotional tribute to her “beloved” husband on Tuesday.
She said: “Stefan’s family wants to express their gratitude for the support and warmth received in recent years, and to express their deepest sympathy to the many friends and fans of Stefan Karl.”
She added that there would be no funeral, instead “his earthly remains will be scattered in secrecy in a distant ocean”.
LazyTown ran between 2004 and 2007 and was briefly revived between 2013 and 2014.
It followed the adventures of Stephanie and her superhero friend Sportacus and their attempts to get the town’s population active.
Robbie Rotten spent his time trying to undermine their plans.