Of course you could argue that all of the Pixar movies are Machinima and I would have to say that you're probably right.
Pixar movies are the complete opposite of machinima. Every frame of a Pixar movie is rendered offline, sometimes taking days. Every movement of a character is controlled by directly controlling the skeleton and skin of the character, and the animator is expected to create precisely the movements required to get the shot.
Machinima is rendered in realtime, it's controlled using a library of animations, and it really couldn't be a more different process.
Matt Kelland
Moviestorm Creative Director& Short Fuze Founder