The idea of creating "Karlson Who Lives on the Roof" was suggested to the writer by her daughter. Once Astrid heard her story that when the girl was left alone, a small cheerful man flies into her room through the window, who hides behind a picture if adults enter. So Karlson was born - a handsome, intelligent and moderately well-fed man in his prime.
Karlsson is called Karlsson på taket in Swedish.
According to the Swedish Wikipedia (http://sv.wikipedia.org/wiki/Karlsson_p%C3%A5_taket), the Soviet cartoons about the Kid and Karlsson were the first adaptation of Astrid Lindgren's immortal work. Unfortunately, only two of the three books were filmed.
By the way, Freken Bok in the Soviet cartoon was drawn in the image of Faina Ranevskaya, who voiced this role.
In Sweden, the surname Carlson is the third most common. In 2008, there were 201, 681 registered carriers of this surname in Sweden.
At home, in Sweden, Carlson is not liked, considering him "a boor, egoist, deceiver, braggart and instigator."
The books do not mention the name of Carlson, he calls himself everywhere simply "Carlson".
The heirs of the writer carefully monitor everything related to the heroes of Lindgren's books. Their company Saltkrakan ab is the copyright holder for all of its works (characters and their derivatives).
The theory has spread on the Internet that the prototype of Carlson is the German Reich Minister of Aviation Goering (according to this theory, the propeller is an allusion to aviation, and Karlsson and Goering are also quite well-fed people).
Carlson's syndrome is a psychological feature of children 3-7 years old who have a need for an imaginary friend.
Contrary to the Soviet cartoon, nowhere is it mentioned in the book that Carlson's favorite food is jam. According to the book, Carlson's favorites are meatballs and whipped cream cake.