Quirky film-maker Tim Burton has revealed his cult cartoon The Nightmare Before Christmas was the result of a feverish dream. The director admits the 1993 classic, which has just been re-released in 3-D, started off life as a hallucination. Burton explains, "I had a 108-temperature fever that night... I think that's where you get your best ideas - the ones that kind of come out of your subconscious."