David S. Cohen, now known as David X. Cohen is a former writer for The Simpsons and head writer and executive producer of Futurama. He wrote 13 episodes of The Simpsons and coined the word 'cromulent', meaning 'valid' or 'acceptable', which has entered wide use following its usage in The Simpsons. Known pre-Futurama as David S. Cohen, he changed his name after joining the Writer's Guild of America as there was already another David S. Cohen (The writers guild does not allow members to have the same name). He chose X because it sounded more "sci-fi-ish", though has jokingly said that the X would make him "the David Cohen people would remember". He works with Matt Groening on many projects.