Paraprosdokian

A paraprosdokian is a figure of speech that uses an unexpected ending to a series or phrase. It can be used for joking or for dramatic effect.

Examples:

• "He was at his best when the going was good." -- Alistair Cooke on the Duke of Windsor
• It was a beautiful day in March when I was hit by a bus

A humorous triple is a kind of paraprosdokian.