Among the shows he hosted were the children's show Titten Tei and the radio quiz show 20 spørsmål (20 Questions).
Titten Tei appeared together with Sjonkel Rolf, aka Rolf Kirkvaag.
Karlsen also was the composer of the song of the popular figure Titten Tei (1972), a wooden dummy from the Norwegian children's television given life by Birgit Strøm.