Not sure I'd want another woman's arse on my titties, even if it's Sara's, but there is something rather naughty about the 'double offensive' of it all. My boobs are infinitely better than my boss's, even though she's 15 years my junior.
Mind you, if it had the words, 'Sara's arse goes here'. then that would be even better, because the stupid bovine object doesn't like even mild swearage either.