Len Munnik is best known for his work as a (political) cartoonist for newspaper Trouw and the feminist magazine Opzij. He also makes cartoons and comics for political and civil society organisations, such as Stichting Wakker Dier, the Socialist Party, Keer Het Tij and the unions CNV and FNV. In 1982 he made the comic 'Maissie, de Moord en de NV Rotmachine' with the famous jurist Professor Peter Hoefnagels. His comics for Opzij were collected in the book 'Hoezo Scheef Verdeeld' in 1984. De Harmonie published several books by Munnik, such as the cartoon series 'Kat & Muis' and the pantomime comic 'Paradiso'. He has also made a comic for the Peace Week 2007 called '40 Jaar Vechten Voor Vrede'. Munnik has also worked on several children's books.