I first saw this back in the late '80s, on one of the Tournee of Animation reels. It is one of the zaniest, funnest, heartwarming bits of animation you will *ever* see.
How to describe? In a nutshell: In an age of cheap, computer-aided animation, "Sunbeam" is a reminder that human being used to lavish vast quantities of nuanced creative energy on fleeting flurries of celluloid.
I was so moved back then that I figured out how to play the featured song on guitar, and sang it at a company talent show! It's one of the sweetest invitations to spiritual progress I've ever heard.
Someone else mentioned: You can find it on cartoonbrew.com. This is one for the archives; I hope it stays around for future generations to see.
((2014 01 15 addendum))
Hey! Vimeo has a HD version on-line!:
http://vimeo.com/47898871