"Is you is or is you ain't my baby?" [duplicate]

Is this phrase grammatically correct?

Is you is or is you ain't my baby?

It's from a Tom and Jerry cartoon: http://vimeo.com/40283242 (at 1:30, 2:00 and 3:00).

Solution 1:

It's a 1944 song sung by blues singers, jazz vocalists, & pop singers from the mid-20th century. Sounds more like Fats Waller than Louis Armstrong.

The Wikipedia article says "The phrase 'Is you is or is you ain't' is dialect, apparently first recorded in a 1921 story by Octavus Roy Cohen, a Jewish writer from South Carolina who wrote humorous black dialect fiction."

It's not grammatical standard English, but it's not intended to be. It's a song lyric.

The link to the blog post about grammaticality in Stan's comment is a really good one, so I'm copying it for this answer.