IMDB has this written for the storyline: For the first time ever, Snoopy, Charlie Brown, and the rest of the gang we know and love from Charles Schulz's timeless "Peanuts" comic strip will be making their big-screen debut like they've never been seen before in a CGI-animated feature film in 3D. And if you're yearning for a bit of trivia: This is the first theatrical Peanuts movie in 35 years!
There's also a few still frames below that come with this for you to take a closer look at. It's incredibly impressive what the animators have accomplished. It feels like Charles Schulz drew these.