Moaning Myrtle
Background
Moaning Myrtle is a ghost that lives in the girl's restroom at Hogwarts School of Witchcraft and Wizardry. She was killed by the Basilisk 50 years ago in the girl's bathroom.
During the events of Harry Potter and the Chamber of Secrets (2002) played by Shirley Henderson
Hermione Granger introduces Harry Potter and Ron Weasley to Moaning Myrtle who lives in the girl's restroom. Ron and Harry see the girl's restroom flooding and go inside. Moaning Myrtle tells them someone threw a book at her and Harry picks it up and takes it with him. After Ginny Weasley is brought into the Chamber of Secrets, Ron and Harry force Gilderoy Lockhart to come with them as they go to the girl's restroom and they ask Moaning Myrtle what she remembers before she died. Harry figures out how to open the entrance to the Chamber of Secrets and they go inside.
During the events of Harry Potter and the Goblet of Fire (2005) played by Shirley Henderson
Harry goes to the bathroom where Moaning Myrtle haunts and takes a bath and puts the egg underwater, just as Cedric Diggory did, revealing the hint.
