Flutterbat is upside down because it has an auspicious meaning in Chinese: Bat (蝠) is a homophone of Good Fortune (福), and Upside-down (倒) is a homophone of Coming (到). So an upside-down bat means ‘good fortune coming’!
Animated with music: https://www.facebook.com/groups/MLP.HKBC/permalink/1836052599986821/