Is Harvey real ?
In my opinion, yes, Harvey is real but certainly have some thing that need some analysis.
First, only three people in the movie had "real interaction" with Harvey, Elwood, Dr. Chumley and Wilson.
With Elwood, the bench on the end of the movie is swinging and the gate opened itself. With Dr. Chumley, the doors of the sanitarium opened themselves too and with Wilson the dictionary changed when he was reading.
For me, the only evidence that make Harvey real is the dictionary one because the others can be only imagination. For example, Elwood obviously has problems with drinking and quit his job after his mother's death and Harvey could be a way out of his previous life. Dr. Chumley had a hard day, worried about getting sued and chasing Elwood, and, I think it is mentioned, he was on a bar too...
Although, Wilson was sober and never had any sympathy for Elwood
What do you guys think ?