One of the most epic and consistent parts of Phineas and Ferb was the neverending battles between Dr. Doofenshmirtz and Perry the Platypus. Every episode would bring a new inator, a new ridiculous pet peeve of Doof's, and a new way that Perry would quickly and easily defeat him. It was their thing, and fans can watch them all over again on Disney+.
Their fights provided a lot of comedy for the series, as Doof was usually upset over trivial and un-villainous problems, but they also sparked a surprisingly sweet and caring relationship between the two nemeses. Some battles stood out from the others, either in hilarity or pure grandeur, and these are the best of the best.
Perry Eats The Cheese
In "Lights, Candace, Action!" it came as a surprise to everyone when Dr. Doofenshmirtz proclaimed that he had renounced his life of crime to pursue cheesemaking. It was then equally unsurprising when he quickly reverted back to villainy after Perry ate his entire cheese wheel.
A charming and funny battle scene then ensued between a ridiculously wheel-shaped Perry and Dr. D, and it was a treat to see the monotony of their fights broken up by Perry's unusual shape. The platypus was typically in top form, and to witness one of his weaknesses be the allure of a cheese wheel helped deconstruct his seemingly stoic and invincible persona. And it made for a pretty great fight, too.
The Chess Game
Given that the characters remained static throughout Phineas and Ferb, as the premise was an endless summer, it was surprising and cool to see the older versions of Perry and Doof in "Phineas and Ferb's Quantum Boogaloo" when the episode first premiered.
They fiercely battled it out over a game of chess, and things got heated after Doof tried to cheat during his turn and Perry throws his dentures. As the scientist zooms away on his scooter, Perry follows close behind with the help of his tennis ball walker. The battle may be underwhelming compared to their younger days, but it's a sweet indication that even in old age, the two are up to their usual shenanigans, and it's definitely a fight to remember.
Doof's Legendary Headache
"Crack that Whip" debuted well into season 1 of Phineas and Ferb, and by its arrival, the repetitive nature of Dr. Doofenshimirtz and Perry's battles had been deeply established. The viewer knew what to expect by that point, so it was a refreshing twist when Doof turns out to have a splitting headache in the episode.
Things turn meta and interesting quickly, as Doof tells Perry to just turn off his invention since he knows it would happen anyway. He then says, "I'll promise to be more evil next time," and it's an amusing inside joke that pokes fun at the formulaic nature of Doof and Perry's interactions. Dr. D's insight was one of the first instances of this self-conscious tone that came to characterize the series, and it made for an especially noteworthy battle.
The Fake Perry Incident
One of the best fights between Perry and Dr. Doofenshmirtz didn't even involve Perry at all. In "Misperceived Monotreme," Perry can't escape Candace's attention, and a random zoo platypus wanders into Doof's lair in his stead. And, miraculously, the fake Perry foils Doof's plan even better than the real one might have.
The tension over what's going to happen makes this battle one of the best, as the usual expectation that Perry would obviously triumph was out the window. The viewer had no idea how the fake Perry could win, and this unknown territory led to an epic showdown with real stakes at hand. It's just too bad that fake Perry never got the recognition he deserved.
The Enormous Tinfoil Ball
The one and only tinfoil ball in "The Rollercoaster" set up the Dr. Doofenshmirtz-fights-Perry premise, and the various beats of this initial battle scene were repeated many, many times throughout the series. It helped establish the comedic, exaggerated tone of their fights, and it was the only one ever fully flashed back to, as seen in both "Phineas and Ferb's Quantum Boogaloo" and "Rollercoaster: The Musical!"
It was a defining moment for the show and the relationship between the two, as well as Perry's signature "grrr," and it's memorable for all the right reasons.
Doofapus
Dr. Doofenshmirtz had an interesting sense of logic, and this trait was perhaps expressed best in the episode "Doofapus," when he turns himself into a platypus to get the edge on Perry. Because, apparently, "the best way to beat a platypus was to become a platypus." His words.
Doof may be a genius inventor, but his decision to change from a larger and stronger animal (a human) to a small, cat-sized animal (a platypus) was questionable at best. However, it did lead to an entertaining and unique battle between the two, as well as some sweet platypus-to-platypus bonding moments that could never have happened otherwise.
The Time Loop
In the episode "Last Day of Summer," Candace accidentally creates a time loop, and Doof finds himself stuck in an endless cycle with Perry. By the end, he realizes that he's not a villain at heart, and he decides to truly join O.W.C.A. It's an interesting last battle, as their fight is repeated over 20 times, and it culminates into a final homage to the "loop" of battles they were stuck in until Doof's change of heart.
The battle was quite epic in scale and complexity, and it was a fitting end to the intricate and deep relationship that Perry and Dr. D shared within the series. Plus, the montage came with a brand-new song, Disney style.
Perry Gets Serious
Perry never took Dr. Doofenshmirtz too seriously until the episode "Journey to the Center of Candace." As he prepared to fight in his typical fashion, Doof unwittingly threatens Phineas and Ferb, and it's a serious mistake. Perry takes him out in a flash, handcuffs him, and calls the police.
It's the only time that Perry ever turns his nemesis into the cops, and it's also the quickest he ever defeated him, as he usually let Doof monologue and entrap him to his heart's content. This battle reflected the instinctual protection that Perry had over the boys, and it also represented the affection he must have held for Doof to indulge him in all those previous "captures."
The Talk Show
The best part of the battles between Doof and Perry was the close, emotional relationship they ended up forming by the end of the series, and the episode "It's About Time!" took it to that next level. The two end up on the show Dr. Feelbetter to talk about Doof's "affair" with his ex-nemesis Peter the Panda, and they make amends after Doof promises to hurt Perry "in the right way."
After this promise, Dr. D unveils a new villainous plan, and he and Perry duke it out the old-fashioned way with armchair projectiles and giant freeze rays. The battle is important because it helps express how cartoonish violence often signifies Doof and Perry's love language, and it's a large foundation for the blurred, frenemy territory they eventually fall into by the final season.
Perry The Teenage Girl
"Does This Duckbill Make Me Look Fat?" had one of the best storylines of the entire series: Perry and Candace switch bodies. A simple summary, yet one could easily imagine the hilarious and complicated outcomes that a body swap like this could entail, including the absolute best battle scene between Dr. Doofenshmirtz and Perry.
No one could have ever imagined that Candace and Dr. D would have a fight scene, but this episode made it happen in an amazing twist. Perry the Teenage Girl tries to smack Doof with his tail only to realize he no longer has one, and he quickly has to reevaluate his fighting style. It's a fun, one-of-a-kind duel between the nemeses, and it seriously could have had its own spin-off.