Small-world theory

Which is correct:
I've searched every nook and cranny.
OR
I've searched every crook and cranny.
???
I've seen both.

Here in the NE part of the US I have only seen and heard nook and cranny.

One entry found for nook.

Main Entry: nook
Pronunciation: 'nuk
Function: noun
Etymology: Middle English noke, nok
Date: 14th century
1 chiefly Scottish : a right-angled corner
2 a : an interior angle formed by two meeting walls : RECESS b : a secluded or sheltered place or part

It's 'nook and cranny' here in the UK too. I've never heard of the other version.

Speaking of Spoonerisms (see a few inquiries below) (should I not capitalize the word?) there was a long-running television commercial for a brand of English muffin, where the butter got into all the "nooks and crannies." The running joke around my in-laws' house was something about "crooks and nannies," but I never imagined people would take that sort of thing seriously.

See post above by Whole-Wheat Camel.