Candace recruits the boys and the other neighborhood kids to find out where their big ideas disappear to. Meanwhile, Doofenshmirtz makes an Invis-inator to make the Fireside Girls invisible so he doesn't get disturbed by them.
Tropes:
- Bait-and-Switch: Doofenshmirtz keeps emphasizing that the Fireside Girls can see him when he is pretending he is not home. But instead, he wants to shoot the girls with the Invisinator ray so that he doesn't have to see them, when he could have easily shot himself with it so he wouldn't have to see them.
- Battle Discretion Shot: When Doof gets attacked by the invisible tiger, we only see Perry's reaction. A few seconds later, we see Doof with his lab coat all torn and whipping the tiger and holding a chair like a lion tamer.
- Didn't Think This Through: After Perry the Platypus tries to use an invisible file to escape the invisible cage he's trapped in, Doofenshmirtz opens a trapdoor and releases an invisible tiger. Unfortunately, Doofenshmirtz didn't install the trapdoor inside Perry's cage, so the tiger attacks Doofenshmirtz instead.
- Plus, when Doofenshmirtz accidentally turns invisible, he fails to notice that the device didn't make him inaudible, allowing Perry to attack him by following the sound of his voice.
- Dramatic Irony: The case of the episode. The audience knows why the boys' inventions disappear (Doofenshmirtz is behind it all), but the kids and Candace don't.
- Evolving Credits: Beginning with this episode, in the title sequence, during the lyrics "Like maybe", when the camera does a Staggered Zoom on Phineas, instead of looking stoic, a smile appears on his face.
- Freeze-Frame Bonus: While Candace is talking to Stacy in her room, she has her own bust schedule on the wall behind her.
- Genius Ditz: Stacy may not have the best attention span, but she has a great idea when suggesting to Candace to focus on the invention instead of the boys.Candace: Stacy, you're a genius!
Stacy: Wow, go figure! Could you call my mom and tell her that? - Honking Arriving Car: Linda's car horn honks to signify her arrival, and this is the first time that the gang look away from the big and obvious ride when it becomes invisible.
- Hulk Speak: "Buford loves this!" and "Buford loves cookies!"
- Laughing Mad: Candace does this when runing with a bucket of paint to expose the apparently now-invisible ride.Candace: You'll see. Everyone will see! [laughs like crazy]
- Mundane Made Awesome: Phineas and Ferb at one point make the best of waiting and turn it into a song.
- Now You Tell Me: Candace says this after Ferb explains to her that even doing nothing can have a profound effect on what happens to the boys' invention.
- Puppy-Dog Eyes: The Fireside Girls' "big, pleading eyes", which disturbs Doofenshmirtz.
- Overly Long Gag: "It's back!" "It's gone!" "It's back!" "It's gone!" "Back!" "Gone!" "Back!" "Gone!"
- Spanner in the Works: Not the case of the Invis-inator, but had Doofenshmirtz not turned it into a Disintegrator and it fired the first time when it did, Candace would've won.
- Stealth Hi/Bye: Happens to the big and obvious ride repeatedly thanks to the Invis-inator hitting it.
- Tick Tock Tune: This episode's song, "Watchin' and Waitin'"
, starts off with the sound of a ticking clock that persists throughout the entirety of the song. - Viva Las Vegas!: Perry's entrance to his lair is styled after a slot machine. Perry is obviously concerned about the noise attracting the attention of Candace and Stacy. When he goes to his lair, he finds out that Monogram is heading to Vegas and wants to keep the entrance on theme.
