Since I got HAPPY FEET on Blu-ray disc in the mail today, I watched that tonight. It's a very enjoyable movie, a little long for the story it's telling, but I didn't see it being any darker than any popular cartoon film I've seen in the last 15 or 20 years.
I have to say, however, that as astounding as the movie looked on Blu-ray, by seeing this movie, I now have seen all three films nominated for the Best Animated Film Oscar, and I would have cast my vote for CARS. I thought the animation was more dazzling, and I got more involved with the story. However, I understand why it didn't win. NASCAR offshoots just aren't everyone's cup of tea.