Someone started a great thread over on reddit about words that people mispronounce. In that discussion some funny misunderstood phrases broke out:

1. For all intensive purposes…
   (“All intents and purposes”)
2. She cut off her nose to spider-face.
   (“To spite her face”)
3. It’s a doggy dog world.
   (“Dog eat dog world”)
4. It’s a moo point.
   (“A moot point”)
5. Don’t put her on a petal stool.
   (“On a pedestal”)
6. You are a diamond dozen.
   (“Dime a dozen”)
7. That really bottles the mind.
   (“Boggles the mind”)
8. That’s just an old wise tale.
   (“Old wives’ tale”)
9. I’m peachy king.
   (“Peachy keen”)
10. You’re a spit and image of your father.
    (“Spitting image”)

(from Reddit)