JK Rowling is giving us more insight into another one of the Harry Potter characters. Which one? Author J.K. Rowling is expanding the Harry Potter universe once again.  Rowling has penned a new short story on her Pottermore website, this one revolving around a character whose name is mentioned just three times throughout the entire series.  Celestina Warbeck is a singer whose lyrics cropped up in Chapter 16 of "Harry Potter and The Half-Blood Prince."  Rowling calls her one of her "favorite off-stage characters in the whole series."  In addition to learning more about Celestina's backstory, visitors to Pottermore can also listen to her hit "You Stole My Cauldron But You Can't Have My Heart," said to be inspired by real-life Welsh singer Shirley Bassey.  Celestina's story can be found in the "Floo Powder Room" on Pottermore.com.