To be honest, super minor characters changing actors doesn't bother me. For example, from the novels we know that Hufflepuff Cedric Diggory was the only seeker to out-snatch Harry Potter but it was due to a Dementor attack in HP's third year. This is shown in the movies and some rando plays the puff seeker (his robe is labeled Diggory but I can't even tell you what he looks like). Diggory becomes an important character in the next movie so he has to be recast based on the level of importance. Maybe that rando was just some extra that was there that day. Maybe his ability to read lines was minimal. Maybe he was busy. Either way, his relevance in PoA is so little that a recast doesn't matter to me. I'm going to say the same thing for Lavender Brown. I didn't even know she was in any of the other movies until reading everyone else's comments.

I think for characters that are a little less than minor, it would be a problem. Like if they re-cast Cho Chang between Goblet of Fire and Order of the Phoenix, it would be confusing for the audience. Is she super important? Not really. Should you remember who she is? Yes. So you would have to not only reintroduce her ("Oh hey it's Cho Chang") but also remind the audience why she is important ("Didn't you have a crush on her Harry but she was dating Cedric when she died?") and it gets a little clumsy, IMO. With more major characters like Dumbledore, that isn't necessary. Not only does the age and make-up help Harris and Gambon look really similar (old white guy with a long white bear and spectacles), the character importance to the film made it obvious who he was supposed to be. If that makes any sense!

caitie / puff