He never had an imaginary friend, but sometimes he would talk to the ceiling at night, in his sleep. He'd also point to where they "got in, through the ceiling". This was upsetting for other people, and they would wake him up and ask him what this was all about. But if you were asleep, and you said you knew things -- like where buried treasure was, or the secret for the elixir of eternal life, and someone woke you up and asked you were it was, would you remember?
In his case, he did remember. He was dreaming of marionettes wielded by unseen persons.
Quail Stove Hot