I've had this story in my head for about two years, but only really started developing it maybe 2 months before the actual coding process began. I think I sort of just had a lot of things already in my mind, because most of the writing was just sort of... improvised. I knew I wanted to go from point A to B, but the road along that wasn't really defined.
Yes, Harley Quinn's name is a pun on "harlequin", a type of clown/court jester. A harlequin is also a rabbit species.