Drop Dead Fred was our daughter's imaginary friend. When she was a little over two years she came into our bedroom and said Drop Dead Fred was at the window and scaring her. He kept coming and scaring her and we started to try very hard to understand who or what he was and get rid of him and get some sleep. He was a bear, we were told, and "nice during the day but scary at night."
I wrote a little story about our trials with Fred and a friend who is a screenwriter caught the thread, optioned the story, and with his partner created a whole new story -- I think they liked the idea of a little girl with an essentially masculine imaginary friend, and the title was great. (We never knew where the phrase DDF came from). Once my mother roped off the living room with its newly cleaned carpet when we came to visit with our toddlers - I think that inspired the dog poo scene, but the rest was all the screenwriters and, significantly, Rik Mayall.
People seem to love or hate the movie. We have friends who walked out, but then I keep meeting people who are bonkers about it - one who named her car DDF. I vote with team Mantzoukas and Raphael - Fred was an extension of Elizabeth's own consciousness and it took more than a little chaos to shake off the controlling forces (her mother et al.) that threatened to drown her.