Imaginary friends are a staple of childhood and are a good indicator of a healthy imagination. I had a few, as I recall; and my younger brother Ward even had an imaginary horse called Sir Galahad.
I have a daughter who is about 16 months old and just learning to speak in earnest. Her imaginary friends will be welcome in our house any time, even if one of them is named Beezly. I absolutely refuse to disprove his existence, given Beezly's track record.
(I'd be a bit surprised but not alarmed if my daughter one day has an imaginary friend named Beezly. Imaginary friends are just that -- imaginary, and only someone a few french fries short of the whole Happy Meal is going automatically to assume that an imaginary friend must be a spirit. )