Drop Dead Fred/Fridge

Fridge Brilliance

Janie only attacked Fred because she didn't want to attack Lizzie, who was clearly having some very serious problems.
Small bit of brilliance, but when Fred shows Lizzie the note she wrote her, we can see it's got incomprehensible squiggles on it. One could interpret this as a kid simply pretending to write, but it's clever in two ways. One in that her mother even if she found the letter wouldn't think heads or tails of it, since she won't be able to read it. Two, since Fred is Lizzie's imaginary friend, he is the only one that knows what it says. Which is proven since he enunciated the last two squiggles in what he believes means "promise."

Drop Dead Fred is supposed to be a lighthearted comedy about a woman whose Imaginary Friend from her childhood causes her mischief in an attempt to teach her to confront her childhood fears. However, with the many disturbing implications throughout the film, it could just as easily be about schizophrenia.
It's pretty much shown that the imaginary friends only appear to children who are deeply unhappy. At the end of the movie Fred is shown to now be the imaginary friend of Lizzie's new guy's daughter, indicating said daughter is deeply unhappy.