Miss Marple/YMMV

The books

 * Moral Event Horizon:
 * The in The Body in the Library.
 * The in A Pocket Full of Rye.

The ITV series

 * Hollywood Homely: "A Pocketful of Rye" had the supposedly-plain Elaine Fortescue played by the decidedly beautiful Hattie Morahan, looking her best in fashionable clothes and an elaborate hairdo. Despite this, the other characters were at pains to point out how unattractive she was.

Other adaptations

 * What the Hell, Casting Agency?: The upcoming Disney version is going to star Jennifer Garner, who is about 40 years too young for the role.