Phineas and Ferb both sat under the old oak tree in their old backyard. Now both being adults and having to care for children of their own, they hadn't been there in a long time.

"Man, we haven't been here in such a long time." Phineas said, voicing the narrator's thoughts. "To think that 20 years ago today is the day we built that rollercoaster."

"Why does it always circle around to the roller coaster?" Ferb asked.

"You know what… I actually don't know."

Just then, Isabella walked over to the fence of the yard. "Phineas, we need to go soon. The kids are in the car and- oh." She stopped once she saw the two men sitting under the tree. "Watcha doin, handsome?" She said, smirking.

Phineas laughed at her joke and smiled back at her. "Just like old times, huh Isabella?"

"Yep, just like old times."

Phineas scanned the yard to see something small and teal moving slowly across the yard. It was Perry, now very old and crusty. If this were an episode, it would be playing his theme very slowly.

"Oh, Perry!" Phineas exclaimed. He picked him up off the grass. "Wow, I can't believe he's so old now. Remember when we accidentally switched his body with Candace's? Good times."

"He's probably going to die soon." Ferb remarked. Phineas looked down at Perry sadly. "Yeah, I know. I just wish there was some way to prevent it. Like, maybe make him age slow- wait, that's it! Ferb, I know what we're gonna do today! Man, I haven't said that in a while."

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"And… finished!" Phineas said, admiring him and Ferb's handiwork. "Now all we need is Perry!"

The machine was huge. It was shaped like a giant film camera and had a bunch of levers and buttons on it.

Phineas picked up the platypus and set him in front of the contraption. "This better be quick." Isabella said. "Don't forget, we're leaving soon."

"Yeah, yeah, I know." Phineas responded. "I just need to-"

"Dad?" A small voice said. Phineas turned around to meet the gaze of his son, Percy. "What's that?"

"Oh, Percy! Sorry we're taking a while to get going, me and uncle Ferb just really had to work on something. Come and see!"

Percy hesitantly crossed the gate into the backyard. "Whoah. Is this where you built all your inventions?"

"Yeah, Percy. This is where it all happened. That time we built a rocket, fought a mummy, climbed the Eiffel Tower…." Phineas trailed off.

Percy walked up to the machine and stared in awe. "Whoah. Dad, what's this do?"

"….located Frankenstein's brai- huh? Oh, that's a machine that's gonna help Perry age better! His body will age just as slowly as a humans does! Now if I just turn this on…"

Phineas flipped a few levers and the front part of the machine started to glow with green energy. It sputtered a bit before shooting a laser at the platypus and changing him instantly.

Perry now had less matted fur and his bill wasn't as crusty as before. He looked almost exactly like he did 20 years ago.

"Wow, I can't believe it worked!" Phineas said excitedly. "Can you believe it worked? Perry's going to live much longer now!"

It was then that Perry started to shake. Not from the cold, it was the middle of summer. Phineas frowned at the platypus. "Uh, Perry? You okay?"

There was a sudden pop and Perry was gone. In his place was a tall, strong looking man with brown hair, a teal jacket, and black pants. The man looked down at himself in horror. He made a strange garbling noise that sounded like he was choking. Phineas, Ferb, Isabella, and Percy all stared at the strange newcomer. Who was this guy?

The man made another weird noise, then attempted speech:

"I-I…. me… hu- perssson…." He looked up at the group. "Boys!?"

"Um….." Phineas started. "…who are you? And where's Perry?"

"I-I….. me…" The man cleared his throat. "S-sorry, it's just that I've never spoken English before… um… I am Perry."

The four of them stared at him in shock. "Perry!? Is that really you!?" Phineas exclaimed.

"Um, yes… I think…" Perry said. "It's just that my feet are smaller and I have more fingers… wait, am I human!?" He attempted to step forward and immediately fell flat on his face. The group kept staring as he tried to get up and failed miserably. "This cannot be good." Perry tried to say through the dirt and grass.