The entire movie has been recreated in 3D stereo with a resolution of 4K (3840x2160) at 60fps.
It took years to rework the movie because the original Big Buck Bunny was created for 2D. Most of the scenes had to be modified to work well in 3D stereo. Furthermore, the original movie was made for cinemas and was 24fps; a lot of changes to the animations had to be made to get the correct results.
The creator of the reworked version explains about it on BlenderNation where he also talks about the fact that the entire movie was rendered via an online collaborative renderfarm, BURP, where volunteers provided spare CPU cycles to make it happen.
If you want to see how your computer measures up to playing 4K content in 60 fps you can download the reworked movie from the official homepage — lower resolutions are also available."
Link to Original Source