From the movie iSundae ( phantommoose.com/isundae/ ), this is the song Cheese Soufflé from part 4.
All of the mice are completely stop-motion animated, using Mac software FrameThief. The camera used was a Canon ZR100. Color correction done with Final Cut Express.
Animation took about two days to complete. We recorded the song beforehand, which took around another day. The music track was created with GarageBand.