An interview with Shirley Henderson
Shirley did an interview with About.com, after announcing to Intermission of her come back in the fourth coming Harry Potter and The Goblet of Fire. This is what she had to say on her upcoming role, still as yet to be shot:

You’re doing another Harry Potter? The next one, yeah, I start filming the next one soon. Moaning Myrtle.
Is Harry Potter just a big special effects machine? It is, yeah.My stuff is obviously special effects because I’m being a ghost, but I do have to do all this flying through the air, in these awful contraptions, and it’s rigorous, it’s quite hard work.
You’re in the fourth but no the third? Myrtle’s not in the third, but she pops up in Harry’s bath in the fourth one.
Is it a smaller or bigger role than Chamber of Secrets? I don’t know because I haven’t seen a script yet. I’m waiting on that to arrive.
How do you play a little girl when you’re 37? It’s just how people see you. I think age doesn’t come into acting. I think it’s how you look, and how you look on screen, how your body’s changing, how your face is developing, how each casting director sees you. I mean, obviously I would never get a 14-year-old who wasn’t a ghost. I wouldn’t have been a real schoolgirl in Harry Potter. It’s ridiculous. It’s only because she’s a ghost, and she’s quite pale, and has a strange voice, and she’s old and everything, so with that, that’s a one-off, that’s a different thing altogether. But it’s how people see you, and who they cast you with, who is cast opposite, it’s not really about how old you are.
How important is it to be a part of Harry Potter as far as British culture goes? I don’t know how important it is, but I feel very lucky. I feel very privileged. It’s surprising to me top be a part of something like that. I can’t quite believe it really.
Many Brits identify its place as the biggest English cultural thing. It’s very, very nice to be a part of it.

**Thanks to Wizard News for this