5-year-old Emil Svensson lives with his family on a farm called Katthult. He has got fair hair and blue eyes and looks like an angel, but is not, as he also has a prodigious knack for getting into trouble. Emil is not malicious, but does not think about the consequences of his actions. He even sates at one point that "Hyss hittar man inte på, de bara blir" (eng. "You don't make up pranks, they just happen"). For example, he gives away food - which is meant to be dinner for relatives who will soon come to visit the family - to the poor because in his view they need it more. Other pranks involve locking his own father in the outhouse, hoisting his sister up a flag pole or make everyone believe she is infected with typhoid. Every time Emil plays a prank, he escapes his father by locking himself in a tool shed. This is not a severe punishment for Emil, who likes sitting in the shed and takes to carving a wooden figure during each of his stays. He eventually accumulates 369 of them, save for the one his mother buries because she claims it looks too much like the rural dean.
Emil also proves to be very resourceful. He has a very good hand with any type of farm animal, especially horses.
At one time, he saves Alfred's life when he had blood poisoning. Alfred was near death and the road to the doctor was covered in snow from a severe blizzard. Emil defied the bad weather and traveled by horse and sleigh to the doctor and thus saving Alfred's life.
His parents are Anton and Alma Svensson, Ida is Emil's little sister - a very well-behaved child, unlike him. She has tried to pull pranks like her brother since she wanted to go to the shed, which she thinks is cozy, but she failed. His father, in particular, is often angry with his son, though it has been seen many times he still likes him a lot when he does not make pranks. His mother, however, adores her boy and tends to say, "Emil is a nice little boy, and we love him just the way he is." She also writes down every bad thing Emil does, in a blue book, although, that blue book expands to several blue books. Alfred is the family's farmhand, and Lina is their maid. Alfred, who is very fond of children, is Emil's best friend, whereas Lina dislikes the boy. She is in love with Alfred and pesters him with her wish to marry him, a subject which Alfred tends to avoid.
Emil's father is portrayed as a very typical inhabitant of Småland - for example, he does not like spending money. In Sweden, this is regarded to be characteristic of people from Småland. Church is very important, and the priest is a regular visitor. Alcohol and swearing are strictly forbidden in the Svenssons' house. The books give a vivid impression of Swedish farmers' daily life in the beginning of the 20th century.