Author's note: Thanks to all of you who have read, reviewed, favorited and followed this. It's now time for the epic conclusion...

Chapter Three: A Grand Opening

Stacy Hirano strolled up the path towards the Flynn-Fletcher house full of anticipation for a great day. After all, she was going shopping with her very best friend; what wasn't there to like? With a grin on her face, she rang the doorbell. Not receiving a response, she next walked around the side of the house towards the backyard; if Candace wasn't there either, at least Phineas and Ferb would be and they should know where she was.

Candace snickered as she peered out from behind a car in the street. So far, things were going to her plan, and then once Stacy came back out front, the redhead would be lying in wait to surprise her. Taking care not to be too loud, she crept up to the front corner of her house, poised to jump out.

Meanwhile, Stacy arrived at the back gate to find an empty backyard. Without anyone there to tell her where Candace was, she took matters into her own hands, pulling out her cell phone and calling Candace herself.

Up front, Candace's phone vibrated in her pocket. Fortunately for her, she hadn't turned the ringer back on following their dinner out last night, so she was free to ignore the call and pretend she didn't receive it.

Sighing in defeat, Stacy backed away from the fence and headed towards the front yard. "Fine then," she said, "I'll just have to go to the mall with someone else. But-"

"Wait, what?!"

Stacy froze in sudden shock as Candace jumped out from behind the corner. Not noticing her friend, the redhead continued. "No! Stacy, you can't do that! Well, actually you could, but why would you want to? Are we not-"

Candace ran right into Stacy, who caught her and placed her hands on Candace's shoulders in an attempt to calm the teen down. "Relax, Candy," she said, "I'm not gonna go to the mall with someone else. Unless you want me to..." The redhead shot a glare towards Stacy, convincing her to cut off that line of thought.

"Then that's settled," continued Stacy. "Next question: why on Earth were you hiding from me?"

"Just...never mind," responded Candace, not wanting to divulge her plan. "Come on, let's go." The two friends continued chatting as they began walking towards their day's adventure.

Across the street, things were slowly taking shape in the Garcia-Shapiro backyard. The supporting structure in the foundation had been completed first, and the outer walls of a bouncy castle spanning most of the yard between the concrete porch and the back fence. A smaller rectangle demarcated the "inner section" where a swimming pool would be located inside of it. At the moment, only Isabella was inside of the structure, hard at work installing the "outer section" floor.

"Isabella, can you hear me?" asked a voice over the hanging speakers.

Remembering what Phineas had told her earlier, she pressed the red button near the entrance hatch. "Yes, yes I can."

"Great! Can you come over here now? Ferb says he's ready to put the roof up."

The young girl joined her best friend on the porch, accepting the soda Phineas offered her with a smile. "So that's the intercom system," explained Phineas, waving Isabella into the house. "To use it, you just stand here and push this button," he gestured to a small panel next to the screen door, "or the one next to the entrance back there."

As they continued to talk, Ferb guided a crane along the side of the house, using it to pick up a section of clear roof panels from between the structure and the fence, and guide them into place across the top of the bouncy castle. After getting out to ensure he had it lined up correctly, he plugged the free end of the roof into a receptacle on top of the structure.

Noticing that the roof successfully remained in place, Ferb walked over to the porch and gave his friends a thumbs-up. Isabella grabbed another section of flooring and hopped down the steps back into the structure. She quickly dragged her piece over by the side wall where it was supposed to go.

"I'm going to try out the sound system now," announced Phineas. A familiar riff filled the building shortly thereafter as Isabella carefully lined up the floor section until it slid into the floor and locked in place with a click. Isabella climbed back onto the porch, grabbing a drink of her soda as Phineas and Ferb began to program the controls for the retractable roof.

Noticing that all three kids were momentarily distracted, Pinky the Chihuahua slipped out the back of his doghouse. Quickly working his way around the perimeter of the yard, he slapped on his O.W.C.A. fedora and slid down a hole into his lair, ready to battle the next scheme of Professor Poofenplotz. Just as he planned, Phineas, Ferb and Isabella were none the wiser.

Perry finished drilling a hole through the floor of his trap. Landing on the 39th floor, he quickly made his way through the darkened room, up the stairway, past a metal box and back into Doofenshmirtz's lab. Meanwhile, the mad scientist was having little success operating the Power Drain-inator. "Come on, you stupid machine! Do you think I have all day?"

Doofenshmirtz was interrupted as Agent P tapped him on the shoulder.

"What do you-" Suddenly, realization set it of who it was. "Perry the Platypus! How did you get over there?" He waited a second for a response, during which Perry reached for the self-destruct button. Doctor D quickly swatted him away before jumping away from the machine himself. The nemeses gathered themselves before launching at each other again; Perry got the better of this exchange, tripping Doofenshmirtz into the laboratory wall.

"Time out," moaned the mad scientist. "Because it's time for my secret weapon!" With a flourish, he brandished a pair of night-vision goggles and put them on. Before he could renew the battle, Perry held up a finger, signaling him to wait. The platypus sprinted back into the hallway.

"Yeah, that's right, run away, Perry the Platypus," taunted Doofenshmirtz. But that was not the agent's intent. Instead, he dashed over to the fuse box and pulled a switch, quickly bathing the hallway in light. Perry snuck back into the lab just as its lights turned back on, temporarily blinding his nemesis.

"AAH! GET IT OFF!" yelled Doofenshmirtz, quickly shedding the goggles by throwing them at Perry, who easily dodged the attack. Agent P charged the mad scientist, and they began to trade blows as the Power Drain-inator started to hum in the background. Dr. Doofenshmirtz used Perry's momentary distraction to knock him down with a chop.

"You're too late, Perry the Platypus!" taunted the villain. "It's working, it's functioning properly, and soon-"

Overwhelmed by the sudden power surge, the Power Drain-inator exploded into a shower of components. Doofenshmirtz couldn't help but to slap his palm to his face as Perry strapped on his glider, saluted the mad scientist and flew away.

"And soon, it will blow up. Really?" Doofenshmirtz huffed. "CURSE YOU, PERRY THE PLATYPUSSSSSSSSS!"

Having completed their fun morning of shopping, Candace and Stacy strolled back up Maple Drive.

"So whaddya wanna do next?" inquired Stacy. However, her best friend was distracted, scanning the Flynn-Fletcher backyard for signs of a big idea. Finding nothing, Candace turned back towards her friend.

"I can't see what Phineas and Ferb are doing. That means they must be up to something," mused the redhead. Her suspicions were confirmed as Stacy pointed towards the Garcia-Shapiro yard, and specifically the structure spanning most of it.

"Would you look at that?"

"Yeah, I am looking at that," responded Candace. "And there's only two people who could make something like that!" Dropping her shopping bag, she took off towards Isabella's backyard. "PHINEAS AND FERB, YOU GUYS ARE SOOO BUSTED!"

Candace quickly sprinted around the side of the Garcia-Shapiro house into their backyard. Noticing someone standing on the porch, the older Flynn tried to stop, but was unable to. Candace shrieked as she tumbled down the steps into the bouncy castle, where Phineas and Ferb were hitting a beach ball back and forth. Realizing she wasn't going to stop, Candace grabbed her cell phone and tossed it into the corner before sliding into the swimming pool. Phineas grabbed the phone on the bounce just as Stacy arrived at the entrance.

"Are you alright, Candace?" asked Isabella over the intercom.

"She's fine, just a little wet," responded Phineas as Ferb and Stacy helped pull his sister back onto dry land. The teenagers took a few seconds to look around and take everything in.

"What is this?" asked an impressed Stacy.

"We haven't really thought about a name yet," replied Phineas. "I was thinking maybe the 'Isabella Garcia-Shapiro All Season Recreation Center'-" He stopped as Ferb gave him a look. "Too long? Yeah, I kind of thought so. Maybe we'll just go with 'her new backyard'. It's a long story." Phineas grinned.

His train of thought dropped away as Isabella came back inside and surveyed the situation in front of her. "I'm gonna go eat lunch with my mom, and then since it's about 100 degrees out, you guys can come back here after that. You guys too," she continued, pointing at Candace and Stacy, "if you don't have any other plans."

Stacy looked at Candace, trying to get a read on her thoughts, and could see the gears spinning in her best friend's head.

Realizing that she wasn't actually going to be able to bust her brothers anytime soon, Candace came to a decision. "Stace, you look like you're dying to try this out," she quipped. "So I'm in."

Later that afternoon, the group of friends – now consisting of Ferb, Isabella, Candace, Stacy and Ginger, who her older sister had picked up at lunchtime – were listening to Phineas as he explained all of the features that were built in.

"And the best part is, pretty much everything is adjustable: water temperature, air temperature, depth, bounciness, musical selections, whether the roof is open or closed...That's all done via the control panel over on the house." Phineas reached down to feel the water temperature, and scooped some of the water back over his head, mainly hitting Isabella who was standing closest to him. She slowly backed away and smirked as a thought came to her mind.

"Temperature feels good now, so that should be everything," continued Phineas. "Any questions?"

"Nope," responded Isabella as she pushed herself off the opposite wall and charged at Phineas. By the time the triangle-headed boy turned around, it was far too late as his best friend crashed into him, sending them both into the drink. Candace, Stacy and Ginger all erupted in howls of laughter, with Isabella joining them once she surfaced, while Ferb chuckled lightly.

"That...wasn't a question," huffed Phineas, although even he couldn't keep the smile off his face.

"I never said I had one," replied a smirking Isabella. At this, Phineas lost it too.

Meanwhile, Stacy glanced at Candace, who immediately understood her intent and grinned widely. The teenagers snuck up behind Ginger, and she quickly joined her friends in the pool. Acting quickly, Stacy then grabbed Candace's arm and tried to yank her best friend in as well.

"OH NO YOU DON'T!" bellowed the redhead. After a quick scuffle, both teens tripped over the edge simultaneously and fell in, narrowly missing Ginger who had scooted out of the way just in time.

And that was the scene Perry the Platypus arrived to when he followed the laughter into the Garcia-Shapiro backyard. A giant contraption that only his owners could have made that quickly; Phineas, Isabella, Candace and Stacy engaged in a splash fight in the pool; Ginger exercising her discretion and hanging out off to the side; and only Ferb remaining on dry land. Perry strolled over to the green-haired boy, who lovingly picked him up.

"Oh, there you are, Perry."

The platypus chattered in response. He knew has family was definitely unique, and Perry wouldn't have it any other way.