For a great depiction of a grown-up with friend, that may or may not be imaginary, see the movie Harvey (https://en.wikipedia.org/wiki/Harvey_(film) https://en.

For a great depiction of a grown-up with friend, that may or may not be imaginary, see the movie Harvey (https://en.wikipedia.org/wiki/Harvey_(film) https://en.wikipedia.org/wiki/Harvey_(film)), James Stewart is great in it.