But when you are doing an animated voice, it has to have...

But when you are doing an animated voice, it has to have more energy than usual or it falls flat and doesn't work. For myself, I found that I had to put myself in the same physical or emotional state as Sid, in order to make that voice sound alive and authentic. So if there was a scene in which he was running, I would be running beforehand to sound out of breath. That's important because the audience can tell intuitively if it does not sound real.