Stefán Karl Stefánsson made his screen debut in the 1994 Icelandic television comedy special ‘Áramótaskaupið.’ He went on to make his first big-screen appearance in the 1995 Þráinn Bertelsson-directed comedy film ‘Privacy’ where he played the role of a student. He continued to appear in television specials and films such as ‘Skaupið: 1999’ (1999), ‘Regina’ (2001), ‘Áramótaskaup’ (2001), ‘Stella for Office’ (2002), ‘Litla lirfan ljóta’ (2002), and ‘Áramótaskaup’ (2002). In 2004, he joined the cast of the Icelandic children's television musical series ‘LazyTown’ as ‘Robbie Rotten.’ The series ran for 2 seasons and aired its final episode in 2007. However, the show was revived for 2 more seasons in 2013 before it went off-air in 2014. After starring in ‘Anna and the Moods’ (2006) and ‘Jóhannes’ (2009), Stefánsson portrayed ‘Lárus Skjaldarson’ in the 2011 Icelandic comedy film ‘Polite People’ directed by Olaf de Fleur Johannesson. Apart from films and television shows, Stefánsson had also starred in a number of plays including ‘The Jungle Book’ (1997-1999), ‘Ivanov’ (1998-1999), ‘Little Shop of Horrors’ (1999-2000), ‘A Midsummer Night's Dream’ (1999-2000), ‘Stones in His Pockets’ (2000-2001), and ‘The Cherry Orchard’ (2000-2002). He was last seen in the live-action comedy series ‘Titch and Ted Do Maths’ in 2015.