Speaking of Remus, the first time I read PoA, my mental image of Remus was very much like the actor Michael McShane.
I don’t know why, but Remus was always fat in my mind. Then, years later, I was discussing it with some friends and they all were like WHAT, and told me that the text doesn’t describe him as fat. Which is true. So then my brain’s Remus became Ewan McGregor.
When the PoA movie came out some time later, David Thewlis did a good job, but Remus is still Ewan McGregor in my head.