I'm pretty sure this is a reference to Bakura's favorite card - Change of Heart - which features a girl with one angel wing and one demon wing.

never mind the stunt(s) he pulled(/s) in (-)a certain episode(s) where he turns into a change of heart to help out somehow

(the only one i can think of is... that one time where someone made yuugi's friends into cards for a duel...? i don't remember this show anymore, and i still haven't read the manga :()