(Scene opens up with the camera zooming into the Flynn-Fletcher house.)
Phineas: Ferb, I think we've outdid ourselves today; The ultimate frozen yogurt machine. We have enough frozen yogurt to last the entire summer.
(A little orange lizard peers behind the house.)
Phineas: Huh. (The lizard jumps ahead.) Check that out, Ferb. Hey, there little guy. You want some frozen yogurt? (The lizard flinches.) Yeah, sorry. We don't have mushroom and larvae flavored.
(Ferb pulls some mushrooms out of the ground. He clicks his tongue and motions for the lizard to come to him. The lizard smiles as Ferb gives him the mushrooms, which he happily eats and jumps onto Ferb's shoulder and cuddles his neck.)
Phineas: I think he likes you, Ferb!
Isabella: Hey, guys! What'cha doin'?
(The lizard camouflages itself.)
Phineas: Cool, he disappeared! We found this lizard.
Isabella: Hey, I've seen one of these before. According to the Fireside Girls' Manual, that lizard is a North American chameleon.
Phineas: Then we'll name him Steve.
Isabella: O...kay....why Steve?
Phineas: 'Cause he looks like a Steve.
Isabella: Huh. Can't argue with logic like that.

(Cut to Candace walking in through the gate on her phone.)
Candace: So I'll see you after you teach your guitar lessons.
(Cut to Jeremy on the other end in his bedroom packing up his guitar.)
Jeremy: Yeah, I only have two appointments today.
(Cut back to Candace.)
Candace: "Appointments." Well, all right, Dr. Six-Strings. Good luck with your "patients". (hangs up and giggles) "Dr. Six-Strings." Now that's banter. Heh. (gasps as she sees the giant frozen yogurt machine) Aha! (Steve disappears again) I finally caught you guys! That thing's not going anywhere! You guys are so busted this time! (runs out)
(Steve reappears as his stomach grumbles.)
Phineas: Looks like he's still hungry. Don't worry, little guy. We'll come back with some food. (Ferb puts Steve on the grass and pats him on the head.) I think Mom just stocked up the fridge.
Isabella: I bet Perry's gonna love Steve. Hey, where is Perry?

(Cut to Agent P already in his lair.)
Major Monogram: Morning, Agent P. Doofenshmirtz has been stocking up a lot of high-end sound equipment and musical instruments. In fact, he jut outbid me on this sweet vintage solid-body maple-top guitar.
Carl: (offscreen) Ouch! You totally got sniped!
Major Monogram: Carl! Anyway, we need you to find out what he's up to and put a stop to it. (Perry salutes) Good luck, Agent P. (The chopper comes out of his seat and he flies away.)

(Cut to:)
Doofenshmirtz Evil Incorporated
(Cut to Doof's lab. A knock is heard at the door and he answers. Jeremy appears with his guitar.)
Jeremy: Hi, Mr. Doofenshmirtz.
Doofenshmirtz: Uh, actually, it's Dr. Doofenshmirtz. But, y'know, whatever.
Jeremy: (walks in) Are you ready for your first lesson?
Doofenshmirtz: Oh, yes, yes. Please come in. I have a very special melody that I'd like to learn how to perpetrate—I mean play. (He plays all open strings on the guitar as his daughter walks into the room.)
Vanessa: Hey, Dad. I'm headed out to the— (sees Jeremy) Oh, a guitar player, huh?
Jeremy: Yup.
Vanessa: So, uh, do you know anything by the Scraping Fangs?
Jeremy: Nah. Not really into the heavy stuff.
Vanessa: (disappointed) I'm outta here.
Doofenshmirtz: (examining his sheet music) Ach! Ach! It's so hard to see all these little notes. D-Do me a favor and flick on that light switch.
(Jeremy puts his guitar down and walks over to the light switch. He flicks it on, but a green ray somehow activates and hits Steve.)
Doofenshmirtz: No no no no no. No, this. (showing a lever on the floor) This is the light switch! Ugh! (He pulls the lever) I tried to make it as obvious as possible.
Jeremy: (pointing out the window) But what was that?
Doofenshmirtz: That was just my prototype Gigantinator ray. It's n-nothing to be concerned about.

(Cut back to the backyard where Steve grows in size. When he is humongous, he begins stomping around crushing the frozen yogurt machine. Candace pulls her mother into the backyard as usual.)
Candace: Mom, Mom, I finally caught them! (eyes closed) Ta.... (sees there's nothing there) Dah... AAAAAAAAAAAAAAAHHHHH!!!!!
(Candaces screaming causes Steve to disappear again. He then reappears, but not before shaking the crushed frozen yogurt machine off his foot.)
Linda: Maybe you should take it easy today and run some errands with me.
Candace: But but but—
(Linda walks Candace with her.)

Phineas: Steve's sure gonna love these mushrooms. (realizes he's not there) Steve, where are you? Steve!
Isabella: (looking down) Uh... (she kneels down and picks up a pebble) Guys, look at where you're standing.
Phineas: Whoa! It's a huge footprint.
Isabella: A huge chameleon footprint.
Phineas: Do you realize what this means? Some giant chameleon took Steve!
Isabella: (looking over the fence) The rest of the tracks lead into the city.
Phineas: We're coming to save you, Steve!

(Cut back to D.E.I. where we hear a slow guitar melody.)
Doofenshmirtz: How'm I doing? I rock, right?
Jeremy: Um...heh. What's so special about this freaky guitar solo?
Doofenshmirtz: Well, it all started at the...

Doofenshmirtz: (voiceover) PYRAMIDS OF EGYPT! I traveled there to, you know, discover the hidden secrets of the PYRAMIDS OF EGYPT! And then it hit me! The answer to my quest was staring me in the face. Hidden in those hieroglyphics was a seemingly random series of musical notes. You see, the PYRAMIDS OF EGYPT! were built with the help of alien intelligence. The Egyptians learned how to play a cryptic guitar solo that would summon an alien armada to help them perform feats of mind-blowing power.
(End flashback)

Doofenshmirtz: That mystical melody is now in my very hands. And once I learn to play it, I can summon the aliens to me and I will become overlord of the TRI-STATE AREAAAAAAAAAAAAAAAAAAAAAAA!
Jeremy: Have you considered switching to decaf?
Doofenshmirtz: I'm sorry, I didn't mean to talk all through our lesson time.
Jeremy: Hey, I'm charging by the hour, so knock yourself out.
(Perry flies by in the background.)
Doofenshmirtz: It's just I'm used to doing all the talking with my nemesis. (Perry drops off the chair.) He's a platypus.
Jeremy: Hey, my friends have a pet platypus.
(Zoom in on Perry as he realizes who is with Doof.)
Doofenshmirtz: Is he fierce, cunning, and good with a grappling hook?
Jeremy: Oh, no. Their platypus doesn't do much. (Perry jumps out of the building and takes a plunger and sticks it onto the bottom of the "nose" of the building.) Well, let's take another shot at learning this solo. (Doof plays the riff better.) Hey, doc, not bad. I think you might be getting it!

(Cut to another part of Danville where Phineas, Ferb and Isabella follow the giant footprints.)
Phineas: Hey, the tracks just stop. What's casting this big shadow?
(Steve appears as the others gasp.)
Phineas and Isbaella: Whoa! (They run away but Ferb stays put.)
Phineas: Ferb, what are you doing? Wait a minute. (Ferb opens the bag he's holding and takes out a mushroom, which Steve eats.) It's just Steve! Wow! How did he turn into a dinosaur?
Isabella: Actually, it's just a giant chameleon.
Phineas: But "dinosaur" sounds cooler.
(Cut to Candace waiting in the station wagon.)
Candace: Stupid errands. (The car shakes.) Huh? (A la that famous dinosaur movie, Candace looks in the side-view mirror and sees Steve with the others.) What? AAAAAAAAAAAAHHH!!!
(Steve whimpers and disappears.)
Phineas: I get it. The sound of Candace's scream freaks him out.
(Candace honks the horn. Linda returns with some bags.)
Linda: What's wrong, Candace?
Candace: (coming out of the car and grabbing her mother again) Mom Mom Mom! Dinosaur! Follow me! Ha ha, ha, ha, the boys are so busted this -- Hey, where'd it go?
Linda: Hi, boys. What are you doing here?
Phineas: Looking for Steve, our dinosaur. Can we keep him?
Linda: Keep what?
Phineas: Steve.
(Candace opens a manhole looking for the big lizard.)
Linda: Is he invisible?
Phineas: Yes. Yes, he is.
Linda: Oh, cute. Alright, Candace, let's go home.
Candace: Invisible friends? Uh, pfft! I'm so getting to the bottom of this.
Phineas: It's okay, Steve. Candace is gone. (Steve reappears.)
(Candace opens the door of the car, but the alarm blares causing Steve to disappear and stomp off again.)
Phineas: Steve, wait! Steve!

(Cut back to D.E.I. Perry's wrist communicator beeps.)
Major Monogram: Sorry to bother you, Agent P. We just wanted to let you know we'd be temporarily unavailable. Seems there's a giant dinosaur running amok downtown and Carl wants to go check it out. (Carl leans into the frame wearing a "I Heart Dinosaurs" baseball cap.)
(Doof's guitar is heard playing the riff up to speed.)
Jeremy: (offscreen) Well, I think you've got it.
Doofenshmirtz: (offscreen) Ah, great! Can you give me a hand moving my amplifinator out onto the porch?
Jeremy: Your what?
Doofenshmirtz: It's my omni-directional amplifinator. It will blast my scorching guitar licks in all directions, ripping through the vacuum of space to summon the alien armada that will help me conquer the TRI-STATE AREAAAAAAAA!!! I don't know why I always say that loud.

(Cut to Steve rampaging his way through Danville. Carl and Monogram are observing it, while Carl snaps photos.)
Carl: This is so cool!
Major Monogram: I'd try to recruit him but I don't think we have a hat that big.
(Cut to Phineas, Ferb and Isabella)
Phineas and Isabella: Steve? Steve, where are you?
Isabella: There's no way we can catch him. He moves too fast. Maybe we should just give up.
Ferb: Give up?!? Give up?!? The day may come when we'll give up on fruitless searches after a mere eleven minutes, but that day is not today! The day may come when our favorite reptile may be lost from our memories and his enduring love of mushrooms forgotten, but that day is not today! (At this point, several passersby gather around to hear this speech.) Today we search! We will search for him in the streets, we will search for him in the trenches, we will search for him in the alleys and the mini-malls and the cul-de-sacs of this fair land. We'll search for him in the multilevel car parks and municipal recreational facilities. (A truck labeled British Imports with a Union Jack on it drives up behind him, giving the appropriate patriotic feel.) And we few. We happy few. We small band of brothers — and girl from across the street. We shall not cease 'til he is found!
All: Yaaaaaaay!!!!
Policeman: We'll help ya find your friend! What does he look like?
Phineas: He's a giant lizard about 40 feet tall.
Man: ...Oh. You could have mentioned that up front.
(Everyone leaves.)
Man 2: Yeah, count me out.
Man 3: You're on your own.
Isabella: Steve! Steve, where are you?!

(Cut back to D.E.I. where Doof is shredding it.)
Jeremy: You're really rockin' now!
Doofenshmirtz: The spaceships should be here any minute. And then, it will be time to pump up the volume!
(The amplifinator raises up on a bar.)
Jeremy: (looks at his watch) Well, that's the hour. I'm gonna pack up my gear. I got another lesson across town.
Doofenshmirtz: Okay, but the aliens are on their way.
Jeremy: (offscreen) Okay. Tell them I said hi.
Doofenshmirtz: They're almost here. Oh, look, here they come! Perfect! The crescendo of all my— (Perry finally arrives on cue) Ah, Perry the Platypus. You don't stand a chance against my awesome heavy metal gear! (He presses a wawa pedal and the amp next to him releases a trap.) Ha ha! Get it? Get it? Heavy metal. Like it's...? Ah.

(Cut back to the search party.)
Phineas and Isabella: Steve?
Steve 1: Yes?
Phineas: Sorry. Wrong Steve.
Phineas and Isabella: Steve, where are you?!
Steve 2: (behind a newsstand) Right here. How can I help ya?
Phineas: Uh, I don't think you're the Steve we're looking for.
Steve 2: You might wanna check at the Steve Convention.
(Scene flips to the Steve Convention where a bunch of Steves are gathered outside.)
Steve 3: Hey, Steve!
Steve 4: Cool name, Steve!
Steve 5: Hey, Steve-a-rino!
Phineas: Hmm... (looks one way and smiles) Steve!
All Steves: What?
Phineas: No, no, not you. That Steve.
Steve 6: Aaah! Steve is a giant monstrous dinosaur!
(All the Steves run away from Steve the lizard.)
Phineas: Huh, I guess they don't like chameleons. Nice to see you again, Steve old boy. (The guitar riff is heard in the distance. Steve looks at it and sees that the amplifinator looks like a giant mushroom. He tramples over to the "mushroom".)
Phineas: No, wait! Come back!
(They chase after him.)
(Cut to Doof and Perry)
Doofenshmirtz: Nothing can stop me now! My alien friends, I command you to— (Steve's monstrous hand grabs the "mushroom".) No! Oh, stop! Aaah! (Perry comes out of his trap) This is not working the way it did on paper!
(Perry flips the sheet music upside down and takes the guitar and strums. He plays the guitar behind his head and plays the riff in reverse. Steve covers his ears. The saucers all fly away. Steve eats the amplifinator and Perry jumps on him.) Curse you, (He Townsends the guitar) Perry the Platypus!
(Jeremy returns)
Jeremy: Um, do you wanna pay by cash or check?
Doofenshmirtz: Maybe I could trade you for some evil lessons?
Jeremy: I'll take cash.

(Cut to Steve with Perry on his tail. Steve bends down to eat more mushrooms from Ferb's hand. The gang climb onto his head. He stands up and Perry slides on his tail and the gang slide over his head.)
Phineas and Isabella: Whoa! Woohoo!
Phineas: Oh, there you are, Perry! Alright, Steve, let's go home.

(Cut to the Flynn-Fletcher house.)
Candace: (offscreen) Mom thinks I'm imagining the whole thing! (Cut to Candace's bedroom where she is on the phone and holding a glass of water.) And I know Phineas and Ferb are behind this. (She sets the glass down. It begins to shake just like in the movie.) Huh? (Steve's giant eye appears in the window behind her. She runs downstairs.) MOOOOOOOOOOMMMMMMM!!!

(Cut to outside. Steve leans forward and the gang get off.)
Phineas: Thanks, Steve. (Steve's stomach growls again)
Isabella: Sounds like he's still hungry.
(Steve whimpers.)
Phineas: Don't worry, big guy. We'll be right back with some food.

(Cut back to D.E.I.)
Doofenshmirtz: Ah, what's the point? I'm just going to sit here in the dark and rethink my life. (He flicks the "light switch" off and the Gigantinator reactivates.) Whoops, heh-heh. Wrong switcher. Y'know, I—I can see how that would be confusing.

(Cut back to the Flynn-Fletcher house where Steve is zapped again and shrinks back down to his original size.)
Candace: (zipping out the door with her mother) Look, Mom! See it?! Look at the gigantic dinosaur!
Linda: (looks down at Steve) Uh-huh, don't you think that's a bit of an exaggeration?
Candace: But but but... (sadly walks away)
Phineas: (coming out carrying a giant bag of mushrooms with Ferb) Hi, Mom! Hey, looks like Steve's looking like his old self again.
Linda: So this is your new pet dinosaur?
Phineas: Well, it's actually a chameleon. You said we could keep him, right?
Linda: Of course. I'm sure he'll blend right in. (Steve goes into Ferb's hand and disappears again.)

(Cut to Jeremy in the OWCA headquarters with Major Monogram.)
Jeremy: Okay, Mr. Monogram, now this is a G-chord.
Major Monogram: Uh, actually, it's Major Monogram. You see, I'm in charge of an elite group of secret agent undercover animals who— (clears throat) You don't mind me going on about this, do ya?
Jeremy: Hey, man, I charge by the hour, so knock yourself out.