Tiger's whiskers are made of the same material as hair and nails so they can get just as sharp as human fingernails, but they are not the same as eating ground glass etc and will not kill anyone.
Katie Leung (Jia-Li) previously played Cho Chang, Harry Potter's first love interest. Mark Williams (Father Brown) played Arthur Weasley, father of Harry's eventual bride. They never had any scenes together.
The opening Waltz is Masquerade by Aram Khatchaturian.