Cimorene

That is so annoying, when people disregard canon appearances or descriptions to make the characters fit their mold of what's attractive.

In line with what I commented to another respondent above, I get particularly peeved at people who do story-focused makeovers, like Xander losing weight because he's working more in construction, or Snape suddenly stumbling across a range of haircare products, so that everyone around them thinks, "Okay, *now* he's handsome and worthy of desire!"

Thank goodness I've never seen fics in which people get actual plastic surgery (though I'm sure they exist; just... *shudders*).