"Harvey is a 1950 film based on Mary Chase's play of the same name, directed by Henry Koster, and starring James Stewart and Josephine Hull. The story is about a man whose best friend is apooka named Harvey—in the form of a six-foot, three-and-one-half-inch tall rabbit."
2. Drop Dead Fred
I love this film. "In the 1991 movie Drop Dead Fred, the lead character develops an imaginary friend in order to cope with the psychological abuse that she had received from her mother."
Drop Dead Fred.