Mad scientists and inventors appear in the fiction of Stanisław Lem in the memoirs of Lem's starfaring vagabond Ijon Tichy, collected in The Star Diaries and Memoirs of a Space Traveller, as well as in The Cyberiad. Most of Lem's mad scientist stories fit into the format of stories about unusual inventions, known since the 19th century, most of them are devoid of ironic tone characteristic of most of Ijon Tichy's stories and robots' fables, and they are literary frames for various Lem's theories.