When I first began reading the Harry Potter series, I mispronounced Hermione's name in my head when I read. I pronounced it: 'Her' - 'me' - 'own'. When the film came out and the correct pronunciation was uttered, I was shocked.
It's similar to my experience with the phrase, "Up and Adam". Or should I say: 'Up and at 'em.' Because for the longest time, (I'm talking the first 18 years of my life) I thought 'Up and Adam' was a biblical reference. I thought it meant, 'be the first one to go for it'. And I realize, all of this can have very naughty connotations in that context, but I was thinking of it purely as a motivational thing. When I read the expression 'Up and at 'em' in a book, it nearly blew my mind.
When I was little and I sang 'The Star Spangled' banner, I used to sing about the 'dawnderly' light. I figured it was a word I didn't learn yet. A really hard word. Like an SAT word. I was singing it one day by myself and my mother stopped me: You mean dawn's early light? Well, gosh darn it, I guess I did.
It's funny how your mind can play tricks on you. Ever have an epiphany about a mispronounced word or saying?