Rune Andréasson published his first drawings in Göteborgs-Tidningen in 1938 and was an actor for the Göteborgs Stadsteater in the following years. He became a freelance illustrator in 1942 and has created children's comics since 1944. His first comic was 'Äventyr bland djuren', published in the family magazine Allers (1944-45), which was followed by 'Brum' (1945-67) and 'Åsnan Kal från Slottsskogen' (1945-52) for the Göteborgs-Posten.
In addition, he produced 'Nicke Bock från Skansen' (1948-50) for Stockholms-Tidningen. After that, he made 'Teddys äventyr' for Tuff och Tuss and in his own comic book in 1959-1960, as well as a daily strip. He also made the daily newspaper comic strip 'Lille Rikard och Hans Katt', which ran for 22 years.
Andréasson produced his first television series in 1958, 'Nalle ritar och berättar'. His most famous creation was 'Bamse' (1966), the world's strongest and cutest little bear. The series was highly successful, and has appeared in a cartoons series and comic books. After a few years of doing all the work himself, Andréasson began contracting other artists to do the artwork.
The Spanish artist Francisco Tora took over the artwork of 'Bamse' in 1976, and was succeeded in 1983 by Bo Michanek. Another creation by Andréasson was the blue toy elephant 'Pellefant' (1965-93). Andréasson retired in 1990, and left his comic to the publishing house Egmont.