I Recommend Pleasant
To quote again from the movie:
"Wilson: [reading from an encyclopedia] "P O O K A - Pooka - from old Celtic mythology - a fairy spirit in animal form - always very large. The pooka appears here and there - now and then - to this one and that one - a benign but mischievous creature - very fond of rumpots, crackpots, and how are you, Mr. Wilson?" "How are you, Mr. Wilson?" Who in the encyclopedia wants to know?"
The thing about Harvey is that only Elwood can see Harvey. Elwood talks to him, describes him to the people he meets, speaks for him, listens to his stories.
Other people have no idea what to make of Harvey, much less Elwood. Still, Elwood knows what is true to him.
He also knows that being pleasant is more important than being smart. Smart might explain a great many things, but there's no explaining Harvey. Harvey, who surprised Elwood one day and never left, is beyond explanation.
It is good to have mysteries in life. Pookas included.