Sadly, the first movie released after the Disney Pixar merge was Cars, the lowest rated 
Pixar film of its time, with Pixar’s first Rotten Tomatoes rating lower than 90%. The film was perhaps judge more harshly because it was Pixar, and critics and audiences alike were disappointed that it did not seem to have the same heart. It’s animation was universally agreed to be beautiful, but the story was lagging. Thankfully, a string of heart touching successes followed.
Ratatouille, the story of a rat who wants to be a fine French chef and WALL-E the story of two robots who fall in love on trash ridden earth, were originally seen as a risky production. The premise of a rat cooking in a restaurant had the potential to turn audiences away, and in WALL-E the idea that a kids movie would have no dialogue for over the first half an hour of the movie was seen as very daring, and compared to the hectic and bright movies of the Disney Renassiance filled with fast talking chacters and energetic songs, remarkably undisney. Both films were a roaring success, and both were nominated for multiple academy awards and won Best Animated Feature.
WALL-E was especially beloved by critics, being only the second animated film to be nominated for six academy awards, alongside Beauty and the Beast, and was named Best Movie of the Decade by Tim magazine(Time magazine). But Pixar was not done, the next year they outdid themselves with the smash hit UP, the story of a crotchety old man who floats his house to South America using balloons, the silent montage in the beginning of the movie, chronicalingthe romance between the man and his deceased wife has been credited as the most touching opening scene of all time, and UP was only the second animated movie to ever be nominated for the best Picture Award, again alongside Beauty and the Beast