Bugs' ears are not cute; they are slick.

I have never heard "like a fart in a mitten". I have, however, heard "drifting around like a fart in a marketplace". That, I believe, comes from Yiddish, and is a variant of "like a fart in a pickle barrel", alluding to the tortuous path of a fermentation bubble as it makes its way up in a barrel of pickles. It Yiddish it is "vi a farts im roisl", and according to Maurice Samuel, it was a play on "vi a frantsoiz in Rusland" (like a Frenchman in Russia), alluding to the stragglers from Napoleon's army.