Slightly more on topic though: i don’t think i ever had a stereotypical imaginary friend i thought was real. though i do remember believing monsters under the bed being a thing, a real terror when you had a captains bed (bunk bed but with a desk/cupboard/drawers instead of the bottom bunk) because there was actual proper room for there to be one 
Imaginary people in imaginary worlds though, i can remember having that since my earliest memories and still do to this day. feels like i’d make a good author if i happened to possess any literary talent whatsoever 