The Professor dreams he had made three normal little girls after realizing all of his successes are mere accidents.
Why It Goes Oopsie With A Capital O
It's just a filler episode of the Professor dreaming of him having three perfect girls when realizing his mistakes, even though the accidents made the girls be able to fight crime and stop evil, which was what the show was great for (At least, in the first 4 seasons).
Speaking of which, the Run of the Mill Girls are just your generic girly stereotypes rather than crime-fighting heroes. To add further insult to injury, their physical appearances are based on redesigns that Craig McCracken briefly considered for Blossom, Bubbles and Buttercup in response to negative reactions from the test audiences for the What A Cartoon! pilots.
That infamous moment where the girls just stared at the Professor for 15 seconds.
Plot Hole: Since when did the Professor work at a pizza place?
Once again, the Mayor still can't open his pickle jar even in a different universe.
Ms. Keane said that the class was going to have a Career Day talk but it was helping the Mayor open his pickle jar, which is not supposed to be the announcement of the said event.
The girls do not even feel remorseful to the Professor when he's sad.
The Powerpuff Girls with different personalities seemed creative, despite the poor execution.
There is some continuity referenced from the season 1 episode, "Uh Oh Dynamo" when the girls mentioned to the Professor about Powerpuff Dynamo being an intentional invention he created that destroyed Townsville.
Good Ending: The Professor wakes up to see the real girls again, accidentally dropping another potion of Chemical X and says, "Oops, I did it again".