So apparently cats can exploit their caretakers to get what they want through the use of a special purr. I can't say I'm surprised, that's a picture of two of my old cats there (rest in peace, guys). One minute they were purring -- and the next I was teaching them how to read!
Researchers at the University of Sussex have discovered that cats use a "soliciting purr" to overpower their owners and garner attention and food. Unlike regular purring, this sound incorporates a "cry", with a similar frequency to a human baby's. The team said cats have "tapped into" a human bias - producing a sound that humans find very difficult to ignore.
I dunno, I'm not really that big into babies crying. But maybe that's just my fatherly instincts talking. Read: impregnate and run. What can I say -- I'm a nurturer.

Cats 'exploit' humans by purring [bbcnews]