... in that Shrek, having a tendency to take the dog role, gets on well with cats, while Fiona, having a tendency to take on the cat role, gets on well with dogs.

In Shrek II, Fiona gets a dog and Shrek gets a cat.

Cats and dogs is just an arbitrary metaphor i used to label two personality types. I find it disturbing that Shrek appears to be using not just the same personality model (and there's no doubt in my mind that Shrek does use the same basic personality model) but the same metaphor.

*demented giggle*

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