Designated Villain: Prince William is a strong (and probably deliberate) example of this; the fic plays him as a despicable villain, but his only crime seems to be objecting to his wife openly lusting after a cartoon cat. Likewise, in the sequel, Prince Harry's only motivation is wanting to avenge his brother.
Squick: The ending which involves Garfield having sex with Kate Middleton. Even laconic as it is, it's rather gross.
It gets worse in the sequel, where Garfield has a threesome with Kate and her sister Pippa, which includes them making out with each other for Garfield's pleasure.