I still think it's weird how they handled Harry's classmates in the Harry Potter movies.
For whatever reason, the first movie only introduces Harry's male classmates (sans Hermione). We meet Dean and Seamus and Neville, but Lavender and Parvati are nowhere to be found.
Parvati doesn't show up until Movie #4, where she is Harry's date for, um...five to ten minutes? Then she disappears. Lavender isn't introduced until Movie #6. It frustrates me that the female characters don't get introduced, until their minor romantic subplots.
True, there's little point in introducing Lavender and Parvati earlier, because they aren't important characters in the books. But that's also true of Dean and Seamus, who are doomed to live their lives as background props for the rest of the movie series. And odds are that being a living prop for a series in their teens will be the high point of their respective acting careers.
I kind of wish the movie series had gone the route of certain TV shows and gone for bold, ridiculous moves like "give Oliver Wood a huge part, because his actor is popular". True, I would have flipped my lid at the blatant disregard for the book series, but it would have been interesting in a train wreck sort of way.