My middle name is the same as my father's first name. I assumed that this applied to everyone. When my friend Alan told me he didn't have a middle name I told him it would be the same as his dad's first name. Alan therefore believed he had the middle name Michael for many years.
A childhood belief about names

others believed things like this
- I used to believe my middle name was and. At age 12, I discovered that it was actually "ann".Anon
- I used to believe that my middle name was Goofy, even though it's actually Margaret.— Lisa
- I used to believe that everyone had the same middle name as me... Elizabeth.
(even my uncles)— K.O. - I used to believe that the red thing in the middle of a Greek olive was the pit.— Liz
- I used to believe my middle name was spelled "Worn" it is "Warren"— Bart
- I used to think the reflectors in the middle of roads were pieces of cheese!Anon