One meaning of "crook" in Australian slang is "to be sick". Rookwood is the name of a huge general cemetery in Sydney. Hence, to be "as crook as Rookwood" is to be pretty bloody sick!
I was pretty surprised when I visited Rookwood to find that real rooks (or ravens, or crows; some blackbirds anyway), do indeed believe it is Rook Wood! (There's a bit on the Wikipedia entry about how it might have got its name - nothing to do with birds mentioned)
On this grave in the Macedonian section, I love the Santa snowstorm and mug.
For some more birds, and pics of the Chinese and Islamic sections of the cemetery, have a look at my additional photos here.