This one was hard. So hard that I couldn’t actually choose just one, it had to be a group.
The Fellowship from the Lord of the Rings series. There’s not one actor I would replace. They all work, they’re all perfect, I will plug my ears if anyone tries to disagree(okay, not really but I’d think of doing it). I have my favourites within the Fellowship(hello Merry and Pippin) but the whole cast just worked so well for me. It’s a huge part of the reason I’ve seen the trilogy so many times. Other than they’re awesome.