It says alot about the Professor that he saw the Black PPG he created as an imperfect prototype even with the three girls he created on accident.
Would this mean that he mixed some other chemical with sugar, spice, and everything nice to create Bliss? Or did he miss out on one of the three components when mixing Bliss? This feels like an afterthought, and would've rather had just heard that a different scientist in Townsville or elsewhere made the same flub-up when making their own PPG than have it be the Professor's past failure he discarded in the bin before he found that his failure with the original three PPG's turned out better than he thought.