When the jedi are being hunted down, Yoda, it was rumoured, covers himself in mud and hops onto Chewbaccas shoulder where he would supposedly impersonate a pet complete with sound effects to make him appear just to be a harmless pet with wind.
Edit: the whole absurd idea (as if the troops wouldn't recognise the great Jedi general Yoda anyway) was probably someone reacting to this shirt
http://shop.starwars.com/catalog/pro...;pcid1=;pcid2=