I Can't Believe It

For those who don't live in the UK there is a product here which you may or may not have heard of. It's a margarine called "I can't believe it's not butter". I believe it was originally from the United States but I have no idea if it's available elsewhere in the world under that name. I don't use it myself but I am quite taken with the linguistic aspects of the latest advertising campaign promoting the new improved version.
It uses the slogan "I can't believe 'I can't believe it's not butter' is better" which it subsequently expands into "I can't believe 'I can't believe 'I can't believe it's not butter' is better' is better than 'I can't believe it's not butter'".

Ain't English wonderful?


And for those who would like more on the subject.