Disclaimer: I don't own Phineas and Ferb or any character from the series.
The Return of Planty the Potted Plant
Phineas Flynn and his stepbrother Ferb Fletcher were at the Flynn-Fletcher living room watching a documentary. "The anemometer." The documentary's narrator said. "The anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics. The first known description of an anemometer was given by Leon Battista Alberti around 1450. Anemometers can be divided into two classes: those that measure the wind's speed, and those that measure the wind's pressure; but as there is a close connection between the pressure and the speed, an anemometer designed for one will give information about both."
While they were watching it, Lawrence Fletcher entered the room. "Hi, kids. What's on the telly?" He asked them.
"A documentary about anemometers, Dad." Lawrence's stepson Phineas answered.
"Really?" Lawrence excitedly asked and joined the boys into watching the documentary. "Cool! These anemometers remind me of the one I made for a school project years ago." Lawrence commented.
"You've built an anemometer, Dad?" Phineas asked out of interest.
"Yes, Phineas." Lawrence answered. "Would you and Ferb like to see it?"
"You still have it, Dad?" A surprised Phineas asked.
"Not with me, Phineas, but I believe my parents keep it somewhere at their home." Lawrence explained.
"Sure, Dad." Phineas answered. "Would you come with us, Pe…? Hey, where's Perry?"
Phineas and Ferb's pet platypus Perry was wearing a fedora hat while inside an elevator with a hedgehog who was also wearing a fedora hat. The two animals then tipped their hats to each other and Perry left the elevator and entered a room where he took a seat next to a seat occupied by a potted plant that was also wearing a fedora hat. He then looked at a screen with Major Francis Monogram at it. "Welcome, Agent P." The man greeted. "Doofenshmirtz is up to something but you have no time for it now. The Regurgitator escaped from prison and we need you to recapture him. Start looking for him at his old hideout. We'll leave Doofenshmirtz for the agent who stopped him while you were handling renegade agent Dennis the Rabbit. Agent P, this is Planty the Potted Plant."
Perry then looked at Planty the Potted Plant and wondered about how a potted plant could have stopped Doofenshmirtz. "He did a good work last time for someone who showed up while the Agency didn't have any agent available. Now take him to Doofenshmirtz's tower and then stop the Regurgitator." Major Monogram ordered.
As Perry the Platypus and Planty the Potted Plant left the O.W.C.A. (Organization Without a Cool Acronym) headquarters, they flew past the Flynn-Fletcher household, where Phineas and Ferb were watching a web generated video of Lawrence Fletcher's anemometer. "Wow! Dad, it's so… small." Phineas said while a little disappointed.
"Well, it was for a school project, Phineas." Lawrence explained. "I don't think they're made much bigger than that.
"Much bigger, huh?" Phineas asked and then stared at Ferb. "Ferb, I know what we're gonna do today!"
Doofenshmirtz Evil Incorporated
Dr. Heinz Doofenshmirtz was at the top of Doofenshmirtz Evil Incorporated Headquarters when Perry the Platypus and Planty the Potted Plant appeared on Perry's flying device. Perry the Platypus then dropped Planty the Potted Plant and left. As potted plants are usually heavier than fedora hats, Planty the Potted Plant fell faster. Planty the Potted Plant then hit Doofenshmirtz and fell on what would be its feet if potted plants had any. Trying to find out who or what hit him, Doofenshmirtz was surprised at what he saw. "A potted plant?" The fedora hat then reached the top of said potted plant. "Planty the Potted Plant?" Doofenshmirtz asked/shouted in surprise. "Planty the Potted Plant, what an unexpected surprise." He commented after recovering from the shock. "And, by unexpected, I mean… well, I suppose I really mean unexpected this time. I was expecting for Perry the Platypus. What happened to him? Oh, don't tell me: the Regurgitator is back and the O.W.C.A. thinks Perry the Platypus should be focused on him, right? Why won't you answer? Oh, right, I told you not to tell me, Planty the Potted Plant. Well, I was expecting for Perry the Platypus but, since you're here…" He then pushed a button and Planty the Potted Plant got caught in the same kind of rope from the first time. "Sorry for repeating the same trap from the last time we met, Planty the Potted Plant. Like I said, I was expecting for Perry the Platypus. Had I known you'd come, I'd have prepared a different trap. Well, I suppose you'd like to know about my new Inator." Doofenshmirtz then exclaimed. "Flashback time!"
Last week, I went to a bar where several single people looking for a date to, well, look for a date. Unfortunately, all girls ignored me until the bartender asked: "Dude, how many women will have to give you the cold shoulder until you get a clue?"
"See, Planty the Potted Plant?" Doofenshmirtz asked. "As those women gave me the metaphorical cold shoulder, I'll give everyone in the Tri-State Area a literal cold shoulder with the (Doof shouted the name) Cold-Shoulder-Inator!" Doofenshmirtz then showed the Inator. "With this Inator, I can give people huge blocks of ice at their shoulders and they won't be able to stand up and then everyone will know what it feels like being given the cold shoulder. But first, I'll keep watching you so I'll know how you escaped last time."
Meanwhile, at the Flynn-Fletcher yard, two delivery boys were bringing stuff Phineas Flynn was receiving. As he signed the proper paperwork, a delivery boy asked "Aren't you too young to build a giant anemometer?"
"Yes. Yes, I am." Phineas answered.
Back at Doofenshmirtz Evil Incorporated, Doofenshmirtz was still staring at Planty the Potted Plant. "You know, I never got the chance to tell Perry the Platypus my reason to destroy the adult diaper factory. Would you like to know about it?"
Back at the Flynn-Fletcher household, Phineas' big sister Candace Flynn showed up and saw Phineas and Ferb building their anemometer. "Phineas, what's this thing?" She asked.
"Did you like it, Sis?" Phineas happily asked. "It's an anemometer."
"I didn't know those things came with seats at their, er, whatever they're called." Candace replied.
"Oh, we installed those to enjoy a ride. Wanna join?" Phineas gladly invited his sister.
"No, but I'll gladly bust you and Ferb for this." She answered. "I'm telling Mom!"
"You should tell Dad this time." Phineas replied. "I bet he'd love seeing the anemometer even more than Mom would."
Enraged at this comment, she left the yard and started dialing her cell phone for her mother when she stopped to think: 'Well, Dad is more likely to know what that thing is, maybe I should call him this time.' She then dialed for Lawrence's call phone.
At Googolplex Mall, Lawrence Fletcher answered his cell phone. "Hello, Candace."
"Dad, Phineas and Ferb are building a giant ane-ni-no, well, one of those things used to measure wind speed." Candace explained.
"You mean an anemometer, Candace?" Lawrence asked.
"Yeah!" Candace exclaimed in joy. "That's exactly what I mean. You and Mom must come home to stop them."
"Candace, I'm sure their anemometer isn't that big." Lawrence reassured his stepdaughter. "Your mother and I will get back home as soon as we finish our shopping."
Meanwhile, at Doofenshmirtz Evil Incorporated, Heinz Doofenshmirtz was finishing telling Planty the Potted Plant about the adult diaper incident. "It was so embarrassing, Planty the Potted Plant. That's why I tried to destroy it. Anything else you'd like to hear, Planty the Potted Plant?"
At that moment, Vanessa Doofenshmirtz entered the lab. "Dad, who're you talking to?" She asked in confusion.
"I'm talking to my new enemy Planty the Potted Plant, Vanessa." Heinz Doofenshmirtz answered. "He came to stop me because Perry the Platypus is too busy with the Regurgitator."
"Uh, Dad, you know Planty is just a potted plant, right?" Vanessa asked in shock.
"Don't underestimate him, Vanessa." Doofenshmirtz replied. "I made that mistake last time we met and he defeated me back then."
"Ooookay." She said and then left, feeling it too weird even for her father's standards.
"Now, where was I?" Doofenshmirtz asked Planty the Potted Plant. "Well, I don't remember, Planty the Potted Plant, so I'll have to tell from the beginning."
Back at the Flynn-Fletcher household, Isabella Garcia-Shapiro appeared and made her famous question: "Hi, Phineas. What'cha doin'?"
"We're building a giant anemometer, Isabella." Phineas answered.
"Cool! May I help?" She eagerly asked.
"Sorry, Isabella, but Ferb and I are already at the last touch." Phineas answered. "However, you may join us for a ride. Would you like to?"
"Sure, Phineas." She answered with hearts at her eyes. As Isabella, Phineas and Ferb started riding, the song from when they started developing their inaction doll started playing.
Meanwhile, Doof finally decided to activate his Cold-Shoulder-Inator. "Well, Planty the Potted Plant, since you have yet to escape, that can only mean you either find my stories entertaining or you were just lucky last time. Since I'm too realist to believe the first option might be truth, I can only believe you were just lucky last time and won't be able to stop me now." Doofenshmirtz then pushed Planty the Potted Plant away like last time. Then, as he was aiming for a target, Planty the Potted Plant bounced back and made him miss. The beam then hit the Regurgitator's right shoulder, making him fall at some equipment and releasing Perry the Platypus. "Curse you, Doofenshmirtz!" The Regurgitator shouted. "Somehow, I know this is all your fault!"
As Planty the Potted Plant hit Doofenshmirtz a second time, it caused a beam to hit the giant anemometer, causing it to shatter. "Wow, I don't know what happened, but I'm glad there wasn't anyone at the anemometer anymore."
As Perry the Platypus went back to the headquarters of Doofenshmirtz Evil Incorporated and saw Doofenshmirtz surrendering. "I surrender, Planty the Potted Plant! You taught me I shouldn't underestimate anyone able to endure my stories." He then noticed Perry the Platypus. "Help, Perry the Platypus." Doof pleaded. "Take Planty the Potted Plant away from here. I'll deactivate my Cold-Shoulder-Inator but please stop him!"
As Lawrence Fletcher and Linda Flynn arrived home, they found Phineas and Ferb building an anemometer that was just slightly bigger than the one built by Lawrence's. "Candace, is this the giant anemometer you were talking about?" He asked.
Still shocked about what happened to the previous one, she answered "No, Dad. The giant one broke and they threw the pieces away."
"Oh, what a fertile imagination." Linda commented. Perry then showed up. "Oh, there you are, Perry." Phineas commented. "Perry, you have no idea of how exciting and surprising our day was."
Perry then made a platypus sound that meant "You don't know the half of it, Phineas"
Bonus story: What if Sergei the Snail had been sent to stop Doofenshmirtz again.
Morning day, Vanessa Doofenshmirtz found her father with baggy eyes. "Dad, what happened?" She asked.
"I stayed awake the whole night waiting for Sergei the Snail to appear so I can explain my new evil plan." Doofenshmirtz answered.
"Sergei the Snail?" She asked in confusion. "But what about Perry the Platypus?"
"He's been reassigned to the Regurgitator and I've been declared a minor threat." He answered. "Because of that, they now send Sergei the Snail to stop me."
"Dad, if Sergei the Snail is, well, a snail, what keeps you from executing your plans before it arrives?" Vanessa asked.
"It's not the same without trapping the hero first, Vanessa." He lamely explained.
"No wonder they find you a minor threat." She commented.
Disclaimer 2: Some data I got about anemometers came from Wikipedia. All I already knew about anemometers (other than what they're supposed to look like) is the fact they measure wind speed.