(Opens up showing the Danville Senior Lodge.)
Isabella: (from inside) Thanks for showing me the old scrapbooks, Nana. (cut to her with Nana and other senior citizens.) I love hearing about the old days. Tell me again about string art. And what was it like to get up and change the channel on the TV?
Nana's Friend: Oh, that's so cute, honey. Look at how old-fashioned I still am. I'm writing a letter. By hand.
Isabella: Why don't you just text or call them?
Nana Shapiro: Hoo-hoo-hoo! You kids know nothing of the lost art of letter writing. Back when we were young, we expressed our truest feelings in letters.
Nana's Friend: Yes. You can tell someone how much they meant to you without worrying about getting interrupted. Or losing your nerve.
Nana Shapiro: Or hiccuping. That was my problem. When I was young, I had a crush on a certain boy, and I wrote a letter telling him how I truly felt. That boy ended up being your grandfather.
Isabella: Wow. I've been wanting to tell someone how I feel for a long time, now.
Nana's Friend: Really? I've got an extra pen and paper!
Nana Shapiro: Now take your time, deeply state your feelings, and express your... (Isabella hands her the paper)
Isabella: I've been scripting this thing out in my head for years.

(Cut to the office where letters get sent)
Nana Shapiro: Perfect time, and the postman's here.
Isabella: Add this to your bag, my good sir. (hands over the letter about her true feelings about Phineas) So Nana, when Grandpa got your letter, did he come running to you and sweep you into his arms?
Nana Shapiro: What? Oh no. I never mailed it. I'm not brave like you. I mean, he would've laughed at me or shown the letter to his friends. Can you imagine the embarrassment?
Isabella: (gets nervous) Oh boy!

(Cut to Phineas and Ferb's garage)
Linda: Hon, why do you have all these boxes of take out food thingys?
Lawrence: It's such a waste to get rid of them. See? Look. Chopsticks and Ponzu sauce. That's Japanese but-but look, there's also a Chinese fortune cookie, that's what's known as fusion.
Linda: Okay. I'm hungry.
Lawrence: Oh. Let's go get some food. Would you kids like to come along?
Phineas: No thanks, dad. We had fusion for breakfast.
Lawrence: All right, then. I'll clear all these drawers and boxes out later, darling. See you, boys!
Phineas: Hey, Ferb! Let's do dad a favor and clear these drawers and boxes out for him! Oh, look at this! It's like a spoon and a fork together! What would you even call that?
Ferb: In the UK, they call that a "foon".
Buford: They do not!
Phineas: It's a perfect fusion of aesthetics and utility. It's like a little work of art. Ferb, I...
Candace: What? What are you doing?
Phineas: Helping dad by clearing out this stuff.
Candace: You're doing a chore? No way are you getting all the parent points. I've got chores to do, too. Carry on.
Baljeet: You know, the drawer in our kitchen is full of honey and catsup.
Buford: Yeah, and ours has red pepper flakes and little tubs of grated cheese.
Phineas: Well, go home and grab it, guys! We're gonna make some art! Hey, where's Perry?

(Cut to Perry)
Doo-bee doo-bee doo-bah
Doo-bee doo-bee doo...
(Perry chatters three times)
Major Monogram: Agent P, it seems that Doofenshmirtz is into astrology now, and that makes him very dangerous to us. I know what you're thinking. I was like you. I always thought horoscopes were a bunch of hooey. But then, I read my own horoscope. I'm a Sagittarius. It said, "It's a bad to get a haircut". How spooky is that? I had my haircut yesterday. Today would be a bad day to get a haircut. How do they know that stuff? If Doof figured out the astrological science of our agents, he could predict our every move!
Carl: Excuse me, sir. I believe horoscopes are meant for entertainment rather to be taken as fact.
Major Monogram: Of course, you think that, Carl. You're a Capricorn. You know what to do, Agent P.
(Perry gets sprung out of his seat)

(Cut to Isabella)
Isabella: (in her head) Oh, come on, Isabella. What's so bad about writing a letter and expressing my feelings? Feelings are natural. Phineas is natural. We are both natural beings in the world. What feelings? (back to normal) Aw. (in her head) Did I really refer to him as "my little crumb cake"? Who does that? (back to normal) Come in, Fireside Girls!
Holly: Go ahead, chief!
Isabella: I just mailed a letter stating my true feelings to Phineas and we need to stop him before he reads it! This mission is top priority! I call it "Operation Crumb Cake"!
Ginger: Crumb Cake? Is that what you called him?
(all laugh)
Isabella: Oh boy, it's worse than I thought.

(Cut to Phineas and Ferb's backyard)
Baljeet: Wow. Artsy.
Phineas: Yeah. We're really getting into it. Who knew that making an art piece out of old take out stuff would be so fun?
Baljeet: It is almost like Tadashi Kawamata's massive chair sculpture in Abu Dhabi.
Ferb: Or the Sub Lyric Pile Killabuster with Onion on Marble in Salzburg, Austria.
Baljeet: Really?
Phineas: Actually, I think he just made that one up.

Doofenshmirtz Evil Incorporated!
(Perry walks in)
Doofenshmirtz: Oh, hello, Perry the Platypus. Could you be a sport and shut the door? It gets really drafty in here. Give it a good slam. Sometimes it sticks.
(Perry falls for Doofenshmirtz's trap)
Doofenshmirtz: Ha ha! Betcha never dreamt you'd get caught in a dream catcher. Actually, Norm made that this morning. Who knew he was so crafty? Anyway, my astrologer believes that when Mercury is in retrograde, anything can go wrong and usually does. And, you know, she's always right, she has dark hair and bangs, and you know, as it turns out, Mercury has been in retrograde all summer. No wonder my evil schemes keep failing! And that is why I invented the Unretrograde-inator! You know, to reverse my bad luck. And I know that Unretrograde is sort of a double negative. It sounds like I'm making Mercury go forwards but I'm actually sending it backwards from going backwards which happens to look forward but it isn't. You know what? Basically, it's a Reverse-inator but... Unretrograde-inator! It sounded more astrology-y. Look. You know, I'll just show you how it works. Oh Norm! Could you come over here for a moment?
Norm: I'm almost finished cleaning up your mid-morning piñata, sir.
Doofenshmirtz: Yeah yeah. Qué bueno, Norm. Now, just stand right there.
Norm: Oki-dokie. (gets zapped by the -inator) Oh my! I have a sudden urge to dump your piñata pieces back on the floor.
Doofenshmirtz: It works!
Norm: Now, I'm going to push the giblets back into the chicken.

(Cut to a street as the mail truck drives past. Isabella, now wearing her Fireside Girl uniform, peeks out from behind a bush, puts on a bike helmet and rides off on her skateboard.)
(Song: "I Need My Letter Back")
Isabella: (singing off-screen)  Postmaster general, please help me out,
I wrote a boy a letter now I'm filled with doubt.
It was a sentimental notion
To spell out my emotion that way
Before I have a heart attack
I need my letter back

I need a retraction, a full-scale rejection,
At least if I could edit it and soften the tone
Please just leave it, I have to retrieve it,
Don't say my opportunity has already flown
Backup singers: Already flown!

Oh, why did I ever sign my name?
I don't want to be forever stamped in shame
I'd have to move to Belgium
And wear a really bad toupee
So before I have a heart attack,
Backup singers: She needs her letter back!
It could be in this very stack
Backup singers: She needs her letter back!
It's hard to overstate this fact:
I need my letter back!

Isabella: We'll never catch them this way! But we will get that letter back! No matter how nicely or politely we have to ask! We'll cut them off at Phineas's house. Let's go!

(Cut to Norm walking backwards.)
Norm: Now I'm going to put food waste back on the dishes.
Doofenshmirtz: (reading the paper) Yes, yes, thank you, Norm. (to Perry) Does this make sense to you? Listen. "Someone is secretly speaking on your behalf."
Norm: (offscreen) Time to unmake the coffee.
Doofenshmirtz: It sounds positive for me, and I like that, but who is speaking nicely of me? Wait, was it you, Perry the Platypus?
Norm: Next, I'll unmake my dream-catcher.
(He takes the dream-catcher off of Perry.)
Doofenshmirtz: No, no, don't do that! (Perry punches Doofenshmirtz.) You never let me finish my sentences.

(Cut to the Flynn-Fletcher house. Isabella and the Fireside Girls run up to the mailbox.)
Isabella: We're in luck! Looks like we're here before the mail's come! Okay, girls! Let's seal off this area! Holly, you go take up a scanning position one half-click to the north! Ginger, you got the south! The rest of you, fan out! We've got to intercept that letter! I'm going in back to keep Phineas distracted. Any questions?
Gretchen: Yeah. How long has this mailbox been here?
Isabella: Oy. (runs off)

(Cut to Norm.)
Norm: Now to unbrush my teeth. What am I doing?! Sir, the effect of your ray has worn off.
Doofenshmirtz: (sarcastically) I'm so happy for you. Listen, could you get this platypus off me?
(Perry flips right off Doofenshmirtz.)
Norm: Wow, is he hard to catch!
Doofenshmirtz: You're just noticing this, huh? Go get 'im!

(Cut to the fence. Isabella walks in.)
Isabella: Hey. (chuckles nervously) So, er, whatcha doin'? (chuckles again)
Phineas: What do you think? The world's largest art piece made entirely of takeout food packets and utensils.
Isabella: Oh, wow! Huh-huh. Artsy!
Phineas: Right? Can I show you around?
Isabella: Sure.
Phineas: Here, Baljeet has thoughtfully recreated Gainsborough's The Blue Boy completely in red pepper flakes.
Baljeet: (revealing his eyes are red, teary and bloodshot) I wish I would have thoughtfully recreated an eyewash station. Sheesh!
Phineas: Watch your step up the chopstick ladder. From here, you can see the whole neighborhood.
(Isabella notices the mailwoman coming.)
Isabella: Phineas, uh...let's switch places. The light catches the foon so beautifully from this angle.
Ferb: (wolf whistles)
(Cut to Ferb holding a cartoony sign with an envelope on it.)
Phineas: Awesome! The mail's here! Wonder if that comic book I ordered arrived. (climbs down)
Isbaella: No no! Wait!
(Cut to the sliding door as Candace walks out.)
Candace: Hey, this doesn't look like a chore to me! It looks like a bust!

(Cut to Holly hiding behind a tree watching the postwoman walk by.)
Holly: (on walkie-talkie) The stamp is on the envelope.
(Cut to the postwoman approaching the mailbox. Milly, Ginger and Katie walk up to her.)
Ginger: Excuse me, but do you have a letter in your bag addressed to Danville resident Phineas Flynn?
Postwoman: (searches in her bag) Hmm, looks like I do.
Ginger: (sternly) We demand that you hand it over to us immediately! (politely) Please?
Postwoman: I'm sorry, it is unlawful for a postal carrier to deliver any envelope or parcel into the hands of anyone except the intended recipient as indicated in the address column of said envelope or parcel.
Holly: What about afterwards? Can we jump him and wrestle it out of his hands?
Postwoman: Honey, what you do with your afternoon is none of my business.
Phineas: (offscreen) Hey, Mrs. Ferguson! (walks up to the postwoman with Ferb) Did my comic book arrive today?
Postwoman: No. Just this letter. (gives it to him)
Isabella: (gasps)
Phineas: Oh, look! It's from you, Isabella!
Isabella: (in her head) Well, Isabella, here it is. He's finally going to know how you really feel. There's no turning back now.

(Cut to Perry climbing on the inator.)
Norm: Come back here! Now I've got-- (Perry spins the inator and it hits Norm.) --rhythm? (Norm falls forward and activates the inator.)

(Cut back to Isabella.)
Isabella: (in her head) At least you told the truth and you spoke from your heart, (smiles) I can accept this.

Phineas: (offscreen) "Dear Phineas..." (cut to Phineas reading) Aw, and there's a little heart.
(Phineas and the postwoman get zapped by the inator. He gives the letter back to her and they walk backwards.)
(Song: "gnoS ykroW ykriuQ")
(While going backwards, Phineas unmakes the giant artwork.)

(Cut back to D.E.I.)
Norm: Oh, no, I just realized I may have put the giblets in the hamster!
(Perry pushes the self-destruct button. To his surprise nothing happens. He ponders for a moment and tries pressing again repeatedly.)
Doofenshmirtz: Ha! Gotcha! See, I began to think, "If only I had a nickel for every time you pushed my inator's self-destruct button", and then it hit me. You wouldn't have a nickel either because you don't have any pockets! Wait, wait, wait, what are you-?! (Perry takes off his fedora revealing a nickel on his head.) Oh, I forgot about your hat. (Perry puts the nickel in the slot.) Curse you, Perry the Pla--
Doofenshmirtz: See?! You never let me finish my sentences!

(Cut to Candace's failed bust.)
Candace: Awww! Of course.
Phineas: Why did I do that?
Candace: (to her mother) There was like a whole bunch of stuff the boys were clearing out!
Linda: Speaking of "stuff", what's up with your room?
Candace: Yep. (walks into the house) I'm on it.
Isabella: Well, I guess we'll never know what was in that letter.
Ferb: (smiling) No, I guess not. And neither will your "little crumb cake."
Isabella: Milly!!
Milly: (whistles innocently)

End Credits

(standalone broadcasts only)
(Song: "I Need My Letter Back")