(Scene opens up showing the Flynn-Fletcher house.)
Linda: What a beautiful summer day. Do you boys have anything exciting planned?
Phineas: We're either gonna make this nuclear-powered submarine or this incredible shrinking ray. But for some reason, Ferb and I can't seem to make up our minds.
Linda: Well, I've made up my mind. (hugs them) You two have the most wonderful imaginations.
Candace: It's real, you know.
Linda: What's real, dear?
Candace: The submarine? The shrinking ray? They're really gonna build that stuff.
Phineas: (walks up) Well, actually we haven't (Candace pushes him away with her spoon) decided yet--
Candace: (talking fast) Anyway, when I try to bust them, everything will just magically disappear. Always happens. you'll see. Well, you won't see. I'll see, trust me.
Linda: (Oblivious) As usual, the imagination in this room is astounding! (walks away)
(Candace's cell phone rings)
Candace: (With the spoon in her mouth) Hello?
Jeremy: (On phone) Hi, Candace. (cut to him) It's Jeremy. I was wondering if you wanted to go for a walk today?
(Candace spits out her cereal then daintily wipes her mouth with a napkin)
Candace: I would very much enjoy going for a walk. Wherever shall we go?
Jeremy: To my uncle's restaurant?
Candace: Yes! That sounds do-able! Why not pick me up around noon? Okay! Goodbye. (hangs up, dials) Oh, my gosh! Guess who just called and asked me out on a date!
Stacy: (On phone) Who!?
Candace: Jeremy!
Stacy: (On phone) Ahh!
Candace: Ahh!
Stacy: (On phone) Ahh!
Candace: Ahh!
Stacy: (On phone) Hold on! Let's conference in Jenny!
Candace: Okay! (dials) Ahh!
Stacy/Jenny: (On phone) Ahh!
Candace: Ahh!
Stacy/Jenny: (On phone) Ahh!
Candace: Ahh!
Stacy/Jenny: (On phone) Ahh!
Candace: Ahh!
Stacy/Jenny: (On phone) Ahh!
Candace: Ahh!
Phineas: (overlapping) Let's go outside!!

(Scene shifts to the backyard)
Phineas: Submarine, shrinking ray. I just can't make up my mind!
Isabella: (offscreen) What'cha doooin'?
Phineas: Oh. Hi, Isabella.
Isabella: (Walks up walking her dog) Hi, Phineas! You remember Pinky.
(Close up of Pinky)
Phineas: (offscreen) Oh, yeah! Hi, Pinky!
Isabella: (Showing her Fireside sash) Hey, check out my new sash! It's got all my accomplishment patches sewn onto it. (holds aforesaid sash in front of him) See?
Phineas: Wow. That looks totally irreplaceable.
(Pinky jumps up and swallows Isabella's sash.)
Isabella: Oh no! Pinky, I need that sash for a Fireside Girls ceremony this afternoon!
Phineas: Don't worry, Isabella, we'll get your sash back.
Isabella: But how? It's in Pinky's stomach.
(Ferb holds up the blueprints.)
Phineas: Hmm... (realizing) Ferb, you're a genius! Hey, where's Perry?

(Camera pans to Perry, who's hiding behind the fence. He puts on his fedora and then enters in a code on a panel. A fence post catapults him, an entrance opens, and he falls into it. After a quick "shot" of him sliding down in a tube, he's in his lair about a minute later.)
Major Monogram: Agent P, thanks for coming. It's Dr. Doofenshmirtz. He's been hiding out in the old abandoned vacuum cleaner factory. You know, at building across town with the giant vacuum cleaner on top? Man, I can't believe that place closed. I blame the Internet. (pause) Your mission, Agent P, is to find out what Doofenshmirtz is up to and then stop him.

(Scene shifts to the garage)
Isabella: So, how are we gonna retrieve my sash?
Phineas: Here. Ferb made this multimedia presentation. We shrink the sub down with Ferb and me in it and put in Pinky's dog food. After he eats us, the sub extrudes two mechanical arms, which fold up the sash to microscopic size and pull it into the sash storage unit. Finally, we pilot up into the mouth and have Pinky drool us out. Easy.
Isabella: Gross, but cool! But Pinky will eat anything but dog food. He likes grilled cheese sandwiches.
(Pinky pants excitedly)
Phineas: Not a problem. You make the sandwich. We'll make the sub.
(Ferb imitates Pinky's excited panting)

Man: Okay. A subatomic shrinking module, hydrostatic ballast tank, and a case of AA batteries. Sign here, please.
Phineas: Aren't you wondering if we're a little young to be building a submarine?
Man: Yes, yes I am.
Phineas: Yeah. We get that a lot.

Isabella: One grilled cheese sandwich, hot off the... Oh, cool!
Phineas: Hey, Isabella. You're just in time.
Isabella: You guys amaze me.
Phineas: When we're inside, we'll activate the shrinkage. You take care of the rest.
Isabella: Check it out, Pinky, your favorite.
(engine whirring)
Phineas: Ready?
(After a blue button is pushed, the submarine shrinks then lands into the grilled cheese sandwich.)
Isabella: It worked! All right, Pinky-Winky, time for some cheesy-weesy!
(A black cat yowls and Pinky's ears perks up. The cat hisses then runs off with a barking Pinky in pursuit.)
Isabella: (While running after Pinky) No, Pinky! Chasing the cat is so cliche! You're better than that!

Candace: (after opening the door to the garage) Listen up! Jeremy will be here any second and I wanna tell you... (notices the grilled cheese sandwich) Ooh, grilled cheese, my favorite. Might as well eat now, so I don't look like a pig on my date.

Doofenshmirtz's Abandoned Vacuum Cleaner Factory!
Doofenshmirtz: Perry the Platypus? I... You know, we always do the same thing. I have a scheme, you try to stop me, I trap you, I tell you my scheme, you escape, then we fight, and I'm defeated. Let's mix it up a little. Let me tell you what. I will tell you my scheme first and then I will trap you! What do you say, huh? Yes, this is much better. Okay, so here it is. The Make-Up-Your-Mind-inator! (chuckles) You know, when you're waiting to order a pizza and the person in front of you can't decide on a topping. Ohh, I hate that! I hate it! (mumbles) I will destroy anyone who can't make up their mind!
(Echoes) Destroy anyone who can't make up their mind!
Phineas: Ferb and I can't seem to make up our minds.
(Flashback ends. Perry becomes enraged)
Doofenshmirtz: Should I go with Make-Up-Your-Mind-inator? Or is that too-on-the-nose? It's funny. Now I can't make up my mind. Oof! (Perry attacks Doofenshmirtz in a frenzy and cuffs him to a wall) Perry the Platypus! What are... Well, I--I did not see that coming.
(Perry clamps the other handcuff onto a pipe)
Doofenshmirtz: Calling headquarters, huh? Hmm. Yes, you—you didn't even give me a chance to trap you.
(Camera pans to a giant snow globe)
Doofenshmirtz: See? I was going to put you in that giant snow globe over there. (Camera switches back to him) Now I have to return it.
Major Monogram: Agent P! What's wrong? Oh! You caught Doofenshmirtz, huh? That's weird. Usually he traps you, then you escape and then...
Doofenshmirtz: We mixed it up a little!
Major Monogram: Hang tight, Agent P. Backup is on the way. I mean, it would be, if we had some. Uh, I'm gonna make some calls.

(Scene shifts to Candace, still in the garage, enjoying the grilled cheese sandwich)
Candace: Oh, yeah. (chewing noisily) This is good.
Phineas: It worked! Pinky's chewing! Prepare for swallowing!
(Doorbell rings)
Candace: (Gasps) Jeremy's here! (Gulps)
Phineas: Whoa! Whaah! (Sonar pinging) Wow. Pinky's neck is really long.

(Scene cuts to the front door)
Jeremy: Hey, Candace.
Candace: Hi, Jeremy.
Phineas: Whoa!
Candace: (Belches) Heh heh. Heh. Excuse me.
Phineas: We did it, Ferb! We're inside Pinky. How about a little road trip music?
(Song: Hemoglobin Highway)
Just the two of us
In an esophagus
It's time to get this mission rollin'
Don't wanna make a fuss
But that was the pancreas
Look down before we reach the colon
On the hemoglobin highway
In a mini submarine
(Mini submarine...)
If you're goin' my way
You'll see what I mean
Hang a left at the spleen...
Phineas: Now to find that sash. Hey, tacos! Ah, tacos. You know who makes the best tacos? Mom. These kind of remind me of the ones we had... for dinner last night. Hey, Pinky didn't have dinner with us. Wait a minute. Candace's favorite cereal?
(Phineas's cell phone rings)
Phineas: Hello?
Isabella: Phineas, where are you? Pinky ran away, and when I came back, the sandwich was gone!
Phineas: Okay, let me call you back. (to Ferb) Yeah, we're inside Candace's stomach.
Ferb: That's creepy on so many levels.

(Scene shifts to the abandoned vacuum cleaner factory)
Doofenshmirtz: (Looking at his watch) This backup of yours is taking forever. (Points to the left while Perry gets up and stretches) I have a travel chess set in my bag over there. (Perry walks in the opposite direction) Do you play chess? (Still pointing to the left) Over there, actually.
(Perry opens the bag to the right, only get trapped by a magnet belt)
Doofenshmirtz: Ha ha ha ha! I tricked you, Perry the Platypus! (Takes a hairpin from his hair then uses it to pick the lock on the handcuff) Do you like my Any-Flat-Surface-Magnet-Belt? It sticks to any flat surface. Hee hee hee hee. Guess what? There's no travel chess set in this bag, either. (gets trapped by the other magnet belt) There was one of these in both bags, so whichever one you chose, you would be stuck. Just like I'm... stuck... right now. What, uh... wh-what time is that backup getting here again?

(Scene shifts to the mini submarine)
Phineas: Oh, here we are. Let's tap into Candace's nerve center so we can see what she sees. Ears. Eyes. Look, we're getting an image. She's on her date with Jeremy. That means we're on a date with Jeremy.
Ferb: Again, creepy on so many levels.
(Candace's cell phone rings)
Candace: Oh, excuse me. My phone is ringing. Hello?
Phineas: Candace, I know this sounds weird, but Ferb and I shrunk down in a submarine. We were in that sandwich you ate, and now we're in your stomach.
(Candace chuckles nervously)
Candace: Are you wacko? Don't call me!
Phineas: Wait! We can prove it! (to Ferb) How do we prove it? "(Ferb pulles up a feather duster to tickle Candace's insides)
Candace: (Laughing) Whoo! Yeah! (Whispering harshly) What is going on?
Phineas: Hey, monkey bars. Do you still get sick when you hang upside down?
Candace: Yeah. Why?
Phineas: Sorry, Candace. We have to help Isabella. So, arms and legs!
Jeremy: Candace, are you okay?
Candace: Heh heh. Heh. Never better. Never better! (straining) Phineas, I'm going to... (Gulps)
Phineas: It's working! All right! Yeah! What happened?
Jeremy: Candace, you sure you're okay?
(Candace gulps)
Jeremy: Come on, my uncle's restaurant is right over here.
Phineas: Any other ideas? "(Ferb pulls out the feather duster again and tickles the inside of Candace's throat)"
Candace: (Coughs, clears throat) I have a tickle in my throat. (Clearing throat)
Jeremy: Stay right here. I'm gonna go get some water.

(Candace coughs out the sub, it returns to normal size and Phineas and Ferb come out)
Phineas: We did it!
Candace: You guys are so busted!
Phineas: Oh, hey, Candace.
(Speed dial)
Linda: (on the phone) Hello?
Candace: Mom, Phineas and Ferb built a SHRINKING SUBMARINE!
Linda: (on the phone) Candace, I'll see it later. Right now, I have to swing by Jeremy's uncle's restaurant and pick up some sandwiches for your father.
Candace: Perfect!

(Scene shifts to the exterior of the abandoned vacuum cleaner factory. Doofenshmirtz leaves it through a boarded-up window.)
Doofenshmirtz: Farewell, Perry the Platypus!
(Perry follows after Doofenshmirtz. The two then uses the magnet belts to reach the top of the giant vacuum cleaner.)

(Scene cuts to Candace running towards Linda , she grabs her just as she was about to lock the car door)
Candace: Mom Mom Mom?! Submarine submarine!

(Scene shifts to the top of the giant vacuum cleaner. Doofenshmirtz's magnet belt snags on the switch.)
Doofenshmirtz: (screaming) (falls into the submarine)
(Perry's magnet belt also snags on the switch, which this time turns the vacuum cleaner on.)
(The giant vaccum cleaner sucks up the submarine)

Candace: See? It's a submarine!!!
(All that's there is only the unveiled sub sandwitch with the "Uncle Joe's Subs" sign on it)
Candace: (facepalms) URRRG!
Linda: So... (walks away) imaginative.

Isabella: Hey, I been lookin' everywhere for you guys! Pinky threw up and I got my sash back!
Phineas: Hmm. Gross, but cool. Speaking of pets...
(Perry chatters)
Phineas: Where ya been, Perry?
Jeremy: Candace, I have a surprise for you. Check it out.
Candace: Sandwich menu? "The Candace Special"? Oh, you had a sandwich named after me?
Jeremy: Yeah. Grilled cheese, 'cause I know it's your favorite.

(Inside the submarine, Doofenshmitz accidentally leans on the blue button. It shrinks and then lands inside the grilled cheese sandwich.)

Jeremy: Shall we eat inside?

(Scene shifts to the interior of the sandwich shop)
Candace: This is the end of a perfect day. My very own sandwich! I can't wait to try it!
(Pinky whimpers, jumps up, eats Candace's sandwich, and then belches.)
Doofenshmirtz: Curse you, Perry the Platypus!

End Credits

(Pinky's in his basket, sleeping and snoring)
Doofenshmirtz: Hello? Where am I? Oh, it's all gastrointestiney in here. Hmm... Brain. (gasps) I'm inside a dog!
(Pinky wakes up in surprise then glares)
Doofenshmirtz: Perfect. Now I can pee all over the Tri-State Area! Ha ha ha ha ha! (sighs) Oh, what am I doing with my life?