I have this headcanon that when Bigby first transformed into a human he was covered in hair and dirt and Snow thought he looked like a complete barbarian. But then after he got shaved and cleaned up, Snow was bringing him fresh clothes to change into and she nearly dropped them because he was standing there naked in all his glory and didn’t seem to mind at all because it’s the norm for him to be without clothes. And she got all adorably flustered and just handed them the clothes and slowly backed out of the room.
And that was their very first moment of sexual tension. (which is why she was all flustered when she saw him shirtless in episode 3 because she was having flashbacks to that moment)