Apparently gone unreported (as far as we can tell) since it’s release in November 2007, there is a bit of news about Pixar’s next film, Up, on the Blu-ray version of Ratatouille. In a scene where Remy is running through the walls of a building towards the rooftop he is chased by a dog, who is only seen in silhouette. During the commentary (not available on the DVD), director Brad Bird points out “this is actually a little guest appearance from a character that will appear in the film after the film after Ratatouille… That dog makes an appearance in the film after WALL-E.” The commentary is part of a Blu-ray feature Disney calls “Cine-Explore” which overlays pictures on the screen relevant to what is happening in the film at that moment or to what the commentators are discussing at the time. You can see a drawing of this dog mentioned during the commentary by visiting the Up thread at the Animated News & Views Forum.
Character from Pixar's Up revealed