Kotaku is reporting that a 14 minute long sequel was made to My Neighbor Totoro called, “Mei And the Kittenbus”. Here is just one photo that rest can be seen in the article HERE
They also go on to say the film is 86% complete will it ever be completed who know Studio Ghibli is not known for doing sequels.
Furry Times 
This is far from a new thing.
This short was done for the Studio Ghibli museum and was shown there for several years.
http://studio-ghibli.wikia.com/wiki/Mei_and_the_Kittenbus
Bootlegs have bounced around the net but where mostly unwatchable.