Karlsson is a fictional character created by Swedish author Astrid Lindgren. He is a mischievous, rotund little man who lives on the roof of a house in Stockholm. Known for his ability to fly using a propeller on his back, Karlsson often gets into various adventures with a young boy named Lillebror. The stories of Karlsson are beloved in Sweden and have been adapted into various forms, including animated films and television series. The character embodies a playful spirit and a sense of freedom, appealing to both children and adults alike.