Due to fallout from Milo time traveling, events occur that result in King Pistachion returning. Allying himself with Dr. Diminutive, the nefarious nut-jobber embarks on a plan to conquer the world and get his revenge on Milo, leading to Milo again having to "crossover" with the inventive stepbrothers to save all of Danville.
Can be read here.
The Phineas And Ferb Effect 2 provides examples of:
- Big Bad Duumvirate: King Pistachion & Dr. Diminutive.
- Crossover: Obviously.
- Failed Attempt at Drama: At the end of the first chapter, King Pistachion attempts to deliver a speech about his plans to get revenge on Milo, but it's ruined because Dr. Diminutive has no idea who Milo is.
- Hand Wave: Melissa asks Cavendish & Dakota how they know about a time abnormality since they were fired from the Bureau Of Time Travel. Cavendish replies that they may no longer work there, but they've retained their knowledge from when they did.
- Noodle Incident: Whatever Milo and his friends go through in the first chapter. All that's known is that it involved lampposts shooting out of the ground.
- Revenge: King Pistachion's goal, next to conquering the world, is getting revenge on Milo for killing him.
- Running Gag: Cavendish refers to the abnormality in time as a "time pocket" which everyone agrees just sounds stupid.
- The subtitle of the story is taken from another sequel involving a villain returning for revenge.
- Timey-Wimey Ball: Essentially, this is the reason given as to why King Pistachion has returned; Milo giving Orton Mahlson the note to give to his friends happened before they defeated Derek, but he is supposed to give the note to them when they fight King Pistachion, which already happened, meaning the note has to be given earlier or they can't defeat King Pistachion, meaning they won't fight Derek, meaning the note can't be given to Orton.