Uli was a rotund little red devil with blue-black hair depicted in German primary school books in the 1970s and the 1980s.
Exercises were based on him, where for example Uli had removed the capital letters or punctuation marks from a text and it was up to the student to replace them.
Uli was created by Ilse Herrndobler who developed the character during her work as a teacher in the 1960s.
Due to the enormous success of the "Uli" school books, the children's book author Ellis Kaut (who created the very popular children's book character "Pumuckl") was asked to write stories based on "Uli" which was followed by the "Fehlerteufelgeschichten" (English: "mistake devil stories") in 1974 with illustrations contributed by Franz Josef Ott.
He also bears resemblance to Titivillus, a demon who serves Satan by introducing errors into type or writing.