two meanings? :S

[InVisible]

does "I've got rats.." just mean I've got rats as pets (in a cage) or anything else...

[Deccius]

I googled the phrase "to have rats", and Google returned this link from a dictionary of slang that was published in the 1890s. The definition of the idiom reads "to have wild or eccentric fancies". Make of that what you will. Given that I've never heard the phrase used and that this definition comes from a dictionary that's over a hundred years old, I think we can safely say that this phrase has become outdated.

[LivingInAmerika]

It can also mean that a person has a rat infestation in their home (Rattebefall?). Most people don't keep rats as a pet, so if anyone ever told me "I've got rats!", I would first assume they mean that there are unwanted rats somewhere in their house or apartment.

The slang from the 1890's doesn't exist anymore, as far as I know of. I've never heard or seen such a slang phrase in my life.