Harvey by Mary Chase

This charming comedy is the endearing story of Elwood P. Dowd, a polite and friendly man who may or may not be crazy, and his best friend and invisible 6 foot 3 inch rabbit named Harvey. Jimmy Stewart starred in the 1950 film version. The play has a lot to say about imagination, faith, and the value of being able to step back from the chaos of life and not take things too seriously.