Off the top of my head, I can think of two things they have in common:
1) the humour: JKR does some delicious parody of British society - pretty much everything in the Ministry of Magic, for example (which presumably translates reasonably well for anyone who has to deal with bureaucracies), and a sly wink at 'facts we all know' such as the reinterpretation of witch burnings. And many of her names are rather corny puns (eg her textbook authors) in a very similar vein to Gromit listening to 'Poochini' and so much else of W&G's visual humour. I'm not sure how well those things translate, though? For example, I remember flicking through an Italian copy of 'Chamber of Secrets' a few years ago and noting that 'Fudge' had been rendered as 'Caramel' (or similar - I can't remember the spelling). I don't think that carries the second meaning of 'Fudge'?
2) both draw on an idealised archetype of British life - Southern/Middle Clasee/defanged boarding school for Harry Potter, and Yorkshire-without-the-rain/Northern/Working Class for W&G. Both steeped in the British perception that we love eccentricity - Arthur and Wallace in particular have much in common.
Whether either of those are particularly exportable traits, I don't know. But both root the material firmly in their originating culture and create worlds that exude a sense of coziness (on first view, at least, with HP), which probably makes any unfamiliar cultural elements more accessible.
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1) the humour: JKR does some delicious parody of British society - pretty much everything in the Ministry of Magic, for example (which presumably translates reasonably well for anyone who has to deal with bureaucracies), and a sly wink at 'facts we all know' such as the reinterpretation of witch burnings. And many of her names are rather corny puns (eg her textbook authors) in a very similar vein to Gromit listening to 'Poochini' and so much else of W&G's visual humour. I'm not sure how well those things translate, though? For example, I remember flicking through an Italian copy of 'Chamber of Secrets' a few years ago and noting that 'Fudge' had been rendered as 'Caramel' (or similar - I can't remember the spelling). I don't think that carries the second meaning of 'Fudge'?
2) both draw on an idealised archetype of British life - Southern/Middle Clasee/defanged boarding school for Harry Potter, and Yorkshire-without-the-rain/Northern/Working Class for W&G. Both steeped in the British perception that we love eccentricity - Arthur and Wallace in particular have much in common.
Whether either of those are particularly exportable traits, I don't know. But both root the material firmly in their originating culture and create worlds that exude a sense of coziness (on first view, at least, with HP), which probably makes any unfamiliar cultural elements more accessible.