Feather of the Phoenix...
Sorry, I must have seemed like I was talking absolute nonsense before! Let me explain...
We know that 2 members of the band Radiohead (Phil Selway and Jonny Greenwood) and also the lead singer of the band Pulp (Jarvis Cocker) have been cast from press reports and the cast list on www.imdb.com. Click
here to see the list in full. imdb.com is usually very reliable and they say if casting is unconfirmed, so we can assume that these roles have been confirmed. I think it was in the newspapers too, but I'm not sure.
The Weird Sisters were introduced in GOF because they played at the Yule Ball. They are one of the Wizarding World's most popular bands. They have also been mentioned as Tonks likes to wear their t-shirts, and one or two of them made minor appearances in a couple of scenes in HBP (I won't say which scenes because of spoilers, but if you want to know which and can't be bothered trawling through the book, please feel free to PM me).
The Weird Sisters are actually all male, not female. They are named the Weird Sisters after the witches in the Shakespeare play Macbeth (Jo being huge fan of this play). At least one of them has been mentioned by name in the Harry Potter books - Donaghan Tremlett - there was an article in the Daily Prophet about him getting married. He was also featured as "Wizard of the Month" on Jo's own website back in July 2004. I also seem to remember them having been described at the Yule Ball in book 4 as very hairy men, but I cannot remember exactly what was said.
I know about the other band members from www.hp-lexicon.org. They have a list of all the characters from the Chocolate Frogs cards found in the Harry Potter computer games. Click
here to see the full list of Chocolate Frog cards and
here to find information on each band member.
Some people might say that the Chocolate Frog cards are not a canon source, and could have been written by anybody, but Jo confirmed on the "F.A.Q. - About the Books" page of her website that she did in fact write all the cards. Sorry, I would post a transcript, but I can't work out how to copy and paste from her site. But it's there if you go and look. I used the information from the Frog cards to write the Snitch's only Weird Sisters
fanfic - just goes to show how sadly obsessed I am! But I love music myself and get the impression that the Weird Sisters are just the type of band I'd love! (Especially if Jarvis Cocker, my absolute favourite songwriter, is writing their music!)
They play rhythm guitar, bagpipes, lead guitar, cello, drums, bass and the lute, and sing. So I'm sure their sound would be very funky and unusual... (Again, with Jarvis writing their songs, they can hardly fail to be unusual! If anyone would like to hear some of his music and do not know any Pulp songs, you can listen to the start of each track
here (His and Hers album), here (Different Class album), and
here (This Is Hardcore album) - this should give you an idea... although he is very versatile, so the Weird Sisters could end up sounding completely different!)
Anyway, back on topic - the casting... if anyone has any pictures at all of these characters, please do post them, as I am dying to see!!!
In the meantime, here are some pictures of how they usually look, for anyone who does not know these musicians.

OMG, I only just realised when I went searching for pics of Jonny Greenwood that he is the member of Radiohead who looks a bit weird (meant in the nicest possible way) anyway! He'll make a brilliant Weird Sister! *squeals* I want to go to a Weird Sisters concert!
There were also
reports originally that Franz Ferdinand were going to be in the band... but they later pulled out. I have just found a really good article scanned and posted on HPANA actually, so here is the
link. Enjoy! And I hope that clears some things up for you!