"Sorry, Candace, but I'm in the middle of the Bridge game", Linda said to her daughter. "I don't have time to go see what Phineas and Ferb have made right now."

"But Mom, you've got to see it!" Candace said, as aggravated as usual. "They made a giant swimming pool, with all sorts of sections and stuff!"

"Honey, aren't you just confusing Vivian maintaining her backyard pool for another of these 'stunts'?" Linda asks, as she placed a 7 of Hearts on the trick on the table.

"No, of course not", Candace argued. "Phineas and Ferb got that request from 11 kids because Isabella's mom is maintaining her pool! You've gotta bust them for it!"

Linda sighed. "Tell you what, Candace", she began. "If you wait patiently and let us finish this game, then I'll go home with you to see this swimming pool, alright?"

"But what if it's gone by then", Candace queried.

"It's either then, or at the end of the afternoon, Candace", Linda said.

"…Alright, you go finish your game", Candace promised.

Meanwhile, Phineas, Ferb and friends have fun with the Loud siblings in the swimming pool. Buford and Ferb went against Lynn and Isabella in a chicken fight, while Luan fought against Leni in a rubber chicken fight. Luna played a rock song during all the fun. Lucy had decided to look over Lily after her swim through the shark pool. Lori and Lola were in the relaxation pool. Lisa was doing experiments in her personal pool, while Lana was brewing soup in hers.

And Phineas was watching Lincoln taking his first cannonball, which delivered quite a splash.

"So, how was it", Phineas asked.

"That… was… AWESOME", Lincoln said.

"That's great to hear", Phineas said. "Now let me try."

The triangle-headed boy climbed up the diving board and cannonballed into the pool like Lincoln, delivering an equally large splash.

"Hey, you're right", Phineas said. "That was amazing!"

"I know, right", Lincoln agreed.

After some fun, the kids were pretty hungry.

"Boy, I could use a snack", Lincoln stated.

"Yeah, I need some fuel after rockin' so hard, too", Luna agreed.

"I dunno if we're allowed to raid Mom's fridge, but I agree that we should go eat something", Phineas said.

"How about we go get some ice cream", Isabella asked.

Everyone agreed in chorus and went to the ice cream parlor.

"Whew, that thing's stored now", Doofenshmirtz said, after he hid the Undo-Inator. He felt a little tired, since he had to push the heavy thing all the way to where he found it.

He panted: "Oof, it would be so much easier if I could undo shoving it to my living room in the first place. Like I… did… earlier… by accident…"

After realization struck, he facepalmed. "Heinz, you Dummkopf", he scolded to himself. "You could've just put in the specific command again! Well, I guess it's too late now…"

He sighed.

"I'll just go back to the living room and with for Perry the Platypus", he said.

As Dr Doofenshmirtz went over to the living room, he found Perry and his four pet friends just busting in his apartment.

Finally, Candace got her mother to get back home, hopefully in time to see the swimming pool before the mysterious force intervenes. Her bike was strapped on the car's roof as the two stepped inside.

"About time", Candace said. "This Bridge game took far too long."

"Don't be ridiculous, Candace", Linda told her daughter. "You sound like you're afraid it might disappear in a second."

"That's exactly what I'm afraid of", Candace complained.

"Candace, you know swimming pools don't just disappear, do you?" Linda asked.

"Under normal circumstances, no", Candace said. She added in her thoughts: "But anything my brothers make gets hidden by this mysterious force anyway…"

"Ah, there you are, Perry the Platypus", Heinz said. "With those troublemaking pets, too. As you can see, I managed to clean up their mess with the Undo-Inator, so with no other interruptions in the way, why don't we continue where we left off?"

Perry agreed with Doof for once, as he decked him in the chin, making the evil scientist fall over.

"Getting straight to the point, eh?" Doofenshmirtz said, standing up. "Let me grab my weapon so we can fight this fairly, OK?"

Perry had no time for this. He already had spent a lot of time to find the pets, so he wanted to end this scheme quickly.

With the respect the Loud pets now had for him, Perry decided a little teamwork wouldn't hurt. He went to Charles and pointed at his nemesis's feet. Charles obliged and went on to bite his ankles.

"YEOWCH!" Doofenshmirtz yelled, being stopped in his tracks.

Perry then went to Cliff and pointed at Heinz's torso. The cat then climbed up to Doof with his claws.

"Ouch, ouch", Heinz said, as he felt the nails in his stomach. He tried to pull Cliff away without avail. "Someone get this cat off of me", he demanded.

Perry then went to Walt, and pointed at Doofenshmirtz's head. The canary flew over to Heinz and perched on his head, poking his forehead repeatedly.

"Ow ow ow ow", Doofenshmirtz said, releasing Cliff, swinging his arms wildly.

Perry then went over to Geo, and pointed at the Grass-Spreadinator at the balcony. Geo ran towards it within his hamster ball and jumped on a few buttons, hoping one of them was a self-destruct button. Unfortunately, these buttons made the device shoot a few rays towards a familiar neighborhood.

Back in the currently deserted backyard of Phineas and Ferb, a green ray had hit the large swimming pool, transforming it and everything inside into soil. The soil fell straight into the remaining hole, fitting it perfectly.

Then another ray hit the soil. The soil's surface got coated with a patch of grass that matched the rest of the yard perfectly, as if nothing had happened.

Geo had trouble finding out which one was the self-destruct button, so he looked with worry towards Perry.

Perry decided to help him, pushing the big red button under the control pad.

With the machine having exploded, Perry went to his hovercraft and gestured to his pet friends to hop inside. Geo followed Perry, as did Charles, Cliff and Walt, releasing Doof.

As they flew away, Heinz yelled: "CURSE YOU, PERRY THE PLATYPUS. AND YOUR ANNOYING PET FRIENDS TOO!"

Phineas, Ferb, their friends and the Loud siblings went back to the backyard. They also met up with Baljeet.

"Yeah, we made a multi-purpose swimming pool for them", Phineas told Baljeet. "Look, Ferb even made a photo of it."

"Ooh, I can not wait to take a swim inside of it", Baljeet said with hope.

As they arrived on the spot, however, the backyard seemed to lack the large swimming pool, deflating Baljeet's hope tremendously.

"OH COME ON", he yelled.

"Hey, where did it go", Lincoln questioned.

"No clue. Nor do we know why it has happened so often this summer", Phineas said.

"Wait, this happens often?" Lincoln gasped.

"90% of the time", Phineas said. "Still no clue how it happens.

"AH-HA", Lisa said. "I knew something odd was about this! I assume there's a fault in your build."

"Well, whatever that may be, Ferb and I haven't found it yet. And we've gone over 150 inventions already this summer."

"There's no 150 days in the summer, Phineas", Lisa said.

"There's not?!" Leni asked.

"Nevermind", Lisa said. "I promise you that I will find out the source of the disappearance of your inventions before the end of the week!"

"…Okay then, good luck", Phineas said.

"Say, um, Phineas, do you know when they disappear?" Lori asked.

"Well, Ferb and I have noticed that our projects always seem to disappear when Candace gets Mom to see our invention", Phineas answered.

Then they heard a car horn.

"Speaking of, they must be here now", Phineas said.

This was followed by Candace dragging Linda to the backyard, saying: "Look, Mom, see? I told you they made a giant swimming pool, I told you-"

Then Candace saw the empty backyard, her eyes growing large in defeat. Her mother oversees the backyard, not quite as surprised as Candace.

"So, where's this swimming pool?" Linda asked.

Author's Note: Again, sorry for the delay. Hopefully, there won't be too much of it when we get to the last chapter of this story. See you then!