Here are what the Academy rules state for the Best Animated Feature Film category:
"If there are 8 to 15 qualified animated features it triggers the category in any given year, and if there are 16 or more the ...
Best Animated Feature Category Might Have Five Nominees
Even though we're not an Oscar blog, that doesn't mean I don't like to occasionally talk about awards buzz. One category of the Oscars that I'm always nervous about is the Best Animated Feature Film category, which usually (and deservedly) ends up going to the latest Pixar feature (which it should this year too), but occasionally ends up going to someone else (like when Wallace & Gromit or Happy Feet won). The category has usually featured only three nominees, but word is that might finally be bumped up to five this year. It's not due to a change in rules, it's simply that there are enough animated movies to allow for five nominees.
