Candace meets another sister with two younger brothers with a knack of building stuff, and the two of them declare a competition over who can build a better fort. Meanwhile, Doofenshmirtz asks Perry to help him win the family kickball game with his Kick-Inator 5000.
This episode contains examples of:
- Accidental Truth: When Candace shoos Linda back to the store, she tells her that she forgot to buy "that stuff". When Linda checks her list, turns out Candace was right.
- Advanced Tech 2000: The Kick-inator 5000.
- Blatant Lies: Vanessa attempts to encourage her father in the game by shouting, "You can do it, Dad!", but she immediately whispers to the crowd member next to her, "He really can't do it."
- Borrowed Catchphrase: Thaddeus takes pretty much all of Phineas's catchphrases.Thaddeus: Well, Thor, I know who we're gonna outdo today.[...]Thaddeus: Hey, where's Harry?Harry: Yo! Ovah here!Thaddeus: Well, he is a contractor. They don't do much.
- Break the Haughty: Thaddeus and Thor become frozen with their jaws agape for the rest of the episodewhen they see the rest of Phineas and Ferb's fort, to the point where their sister claims they "broke their brains".
- Bubblegum Popping: When Phineas and Ferb reveals their own fort, Thaddeus is blowing a bubble with his bubblegum; the fort shocks him so much that the bubble pops in his face.
- The Casanova: Phineas insists they don't invent to compete, but for fun, but Ferb insists...Ferb: And for the ladies. (growls seductively while doing an Eyebrow Waggle)
- Evil Counterpart: Downplayed, the titular Thaddeus and Thor aren't evil, but they're more inclined to brag about their Big Ideas than Phineas and Ferb. Candace also has a similar rival in the form of Mandy, who brags about how her brothers' inventions are better than Candace's brothers'.
- Failed a Spot Check: Although Linda actually sees the Big Idea, she only saw the top portion which looks like a regular plain old fort (a homage to old-school construction); Phineas and Ferb had to hide the rest of the fort underground due to zoning laws.
- Fainting: Candace, when she fails to show Mom the fort.
- Honking Arriving Car: As always, Linda's car horn honks to signal her arrival, but this time, this worries Candace because if she arrives, their invention might disappear as usual, so she tells her to get some "stuff" at the grocery store.
- I Heard That: Candace gives a pep talk to her brothers saying she is not going to lose to two "lame-o" kids and "their loser sister", to which Mandy says, "I can hear you!"Candace: I know! Because I said it loud!
- Informed Flaw: Doofenshmirtz claims that he has no coordination with his feet, but in previous episodes he's known to have a kick line in a lot of his musical numbers and is able to kick in sync with the other dancers.
- Irony: Linda, when she sees the top of Phineas and Ferb's fort (which looks like an average fort; the rest they had to hide due to zoning laws), says "Isn't it great? The boys are starting to take an interest in building things!"
- I Think You Broke Him: When Thaddeus and Thor are left speechless by Phineas and Ferb's fort, Mandy complains, "Nice going, you broke their brains!"
- Jaw Drop: Both Thaddeus and Thor after touring Phineas and Ferb's fort, which turns out to be much better than theirs.
- My Significance Sense Is Tingling: When Candace rapidly stacks all of the groceries, Doofenshmirtz remarks that he senses "a disturbance in the cup-stacking universe. I think my record's been broken."
- Normal Fish in a Tiny Pond: Thaddeus and Thor do seem to be pretty good at construction in an age appropriate way but they are by no means the Impossible Genius Child Prodigy's Phineas and Ferb are.
- Red Herring: At first, it seemed like the boys haven't even bothered to do better than their neighbors and built just an ordinary fort; but then Phineas reveals this is only the top level which is a homage to old-school construction, and Ferb reveals the rest of the enormously tall fort. Phineas tried to tell this to Candace earlier, but she interrupted him and left.
- Screw This, I'm Outta Here:
- Phineas and Ferb's fort is so majestic it is enough to reduce Thaddeus and Thor to silent surprise, prompting Mandy to take them home.
- And earlier, when the fort is at first revealed as a crude run-of-the-mill fort, Candace's response is to simply leave, just before the real fort is revealed.
- Self-Parody: "Snuck Your Way Right Into My Heart" is reworked by Doofenshmirtz into "Kick Her Way Right Into My Heart", complete with an appearance from Love Händel themselves.Doofenshmirtz: How d'ya luke that, Perry the Platypus? Love Händel! In my flashback! I know people.
- "Shaggy Dog" Story: Doofenshmirtz succeeded at kicking the ball when it's his turn in the kickball match, only for the ball to bounce off Phineas and Ferb's fort and into Roger's hands, which rules Doof out and makes everyone at Doof's family reunion cheer for Roger yet again.
- Suddenly Voiced: Doof's mother has her first speaking appearance, voiced by late TV and film veteran Cloris Leachman using a similar accent she used in Young Frankenstein.
- Unknown Rival: Downplayed. Phineas and Ferb recognize that Thaddeus and Thor are trying to compete with them, but are too friendly to get caught up in petty competition. Never feel the need to brag about their inventions and even though they beat them effortlessly in the end they simply compliment them on the liquorish dispenser idea.
- The Voiceless: Thor, not unlike Ferb. Thaddeus does all the talking.
- Was Too Hard on Him: Discussed. Monogram questions what's taking Perry so long to attend his briefing, and Carl suggests that Perry might have quit because Monogram was too harsh on him during his last briefing, which worries Monogram. After Perry does appear and finishes his briefing, Monogram asks Carl if he's too rough on him this time.
- What Happened to the Mouse?: We never find out what happens to the fort, as it was never seen again after this episode.
