When I'm writing a novel, I keep notes on my characters and locations, as I don't want to rely on my memory to keep the facts straight. And you just know, a reader will notice any missteps and take note.
This happened to me when I gave a book I had just finished to a friend to read. "Why did you change the dog's name?" she asked when she returned the book. I remember writing after a break away from it and obviously renamed the dog. I did look up the neighbor's name in my notes when it didn't come to mind.
This is one of the reasons you have readers to read the book and give feedback before the final edit. They often pick up mistakes, in the plot, phrasing, or names etc.
I believe there is a person in the movies and television whose job it is to look for those little bits that don't fit, that break up the continuity of a scene. It can happen easily if you knew the way shows and movies are made. Scenes are not filmed in the order they appear in the finished product.
I was watching reruns of NCIS Los Angeles, and decided they need a new person for this job.
The one today has Detective Deeks gunned down in what was first thought to be a store robbery. They quickly realize he was not an innocent bystander, but was the intended victim. When they tried to figure out who had it 'in' for poor Marty, the comment was made he had no next of kin listed.
Turns out he did have a father, not the best of dads as Marty shot him when he was a kid. I didn't get what reference might have been made about his mother. But moving forward, there's a show where Deeks introduces Kensi to his mother. It would appear they had a close relationship, so where was she when he got shot? Continuity.
Same show, not a character's history this time. A woman Callin knew from his CIA days comes back seeking help. They set her up to meet a rogue CIA agent, at the beach. Being a suspicious kind of guy, he has her walk into the water, to short out any listening device.
She would have been the winner in any wet T shirt contest, as was obvious with the comments Deeks made. But only moments later, she shoots the bad guy, and lo and behold, her shirt is dry. I know it's hot in California, but I don't think clothes would dry that fast.
It's all in the details, and when noticed, whether in a book, a movie or on television, they distract the reader, the viewer from the story. Not a good thing.