A/N: Big thanks to Zoe Alice Latimer for coming up with the idea for this fanfic.

"There has to be a reason why the TARDIS landed here," Ferb said.

Phineas aimed his Sonic Screwdriver at the ground. "No sign of alien activity," he reported. "I know the TARDIS always brought dad where he needed to be, whether he knew it or not, but I have to agree with you on this one, bro."

As if on cue, a 5-year-old girl walked out of a neighborhood house in shock. "Who are you two?" she asked.

"I'm Phineas, and that's Ferb," the 11-year-old boy said. "We're travelers who stopped here for a visit."

"I'm Candace Pond," the girl said, then she noticed Perry. "Who's that?"

"That's Perry," Phineas explained. "He's an alien platypus. His species does a lot of things."

"'Alien platypus'?" Candace repeated.

"We're self-regenerating time-travelers," Ferb said. "We travel throughout time and space, even to different alien civilizations."

"Can I come?" Candace asked. "If you're time-travelers, you can bring me back to the moment I left so no one notices my absence."

Ferb was about to say something when Phineas shushed him. "I don't think so," the 11-year-old boy told Candace as he picked up Perry and dragged his brother inside the TARDIS. "Our time machine only holds three people. Well, two people and an alien platypus, but you really can't come. Bye!"

"What was that all about?" Ferb asked. "Father always had a companion with him."

"I don't want to make the same mistake he made," Phineas explained. "Remember what happened to Ms. Noble? Or what about Ms. Tyler? They were FORCED to leave."

"Ms. Jones left by choice," Ferb recalled. "As well as Ms. Smith. Not all of father's companions were forced to leave."

"I'm not taking that risk," Phineas disagreed. "TARDIS, please take us somewhere else."

After a few seconds, Ferb checked a monitor. "We just went ten years into our previous location."

"Why is the TARDIS insisting we should check out 21st century Danville?" Phineas asked.

As if on cue, another monitor played a clip from one of The Doctor's adventures. Phineas recognized it as the time he and Rose, who appeared to be his favorite companion, went to London in the year 1953. It was when The Doctor found out what happened to Rose after her face was stolen by The Wire.

"Because now, Detective-Inspector Bishop, THERE IS NO POWER ON THIS EARTH THAT CAN STOP ME!"

Phineas realized what the TARDIS was trying to tell him: there was someone in 21st century Danville who was a lot like Rose. "Come on, Ferb," the 11-year-old boy said. "We have a companion to find."

"Says the Timelord who didn't want one to have her entire memory erased..." Ferb muttered to himself.

Sure enough, Phineas, Ferb, and Perry were in the exact same spot. Noticing a mailbox that read 'POND', Phineas knocked on the door. A 15-year-old girl answered it.

"Is Candace home?" Phineas asked.

However, the girl didn't respond. "I think that IS Candace," Ferb told his brother.

Phineas facepalmed himself. "Sorry," he told Candace. "I bet your life is ruined thanks to us."

"Ruined?" Candace asked. "Ever since you three showed up, I've been having dreams where I'm traveling in your time machine to different planets. That lead to me researching the concept of dreams and what they predict. I'm currently an intern working for a dream psychologist."

Phineas sighed in relief, glad he, Ferb, and Perry didn't make the same mistake The Doctor made with Amy.

After a while, Phineas, Ferb, Perry, and Candace were in the living room. Candace was interested in learning about the two brothers and their alien platypus friend.

"Let me get this straight," Candace said. "You two have to travel through space and time because your dad, who did the exact same thing, died after using all of his lives. During your first adventure, you befriended Perry and saved his life before the rest of his species became extinct."

"Yep," Phineas replied. "Now the TARDIS wants us to find a companion like dad had when he traveled."

"Candace, who are you talking to?"

A 10-year-old girl with long black hair and sapphire blue eyes walked in. Phineas looked at her, which made his stomach feel weird and his two hearts to beat faster than usual. There was something about this girl that reminded him of Rose...

"Who's your friend?" Ferb asked Candace.

"Isabella Tyler," Candace explained. "I've been her legal guardian since her parents died in a hospital fire."

Phineas, however, didn't hear any of the conversation. He thought about what The Doctor told Rose, especially what she didn't get to hear.

"I love you," the 11-year-old boy thought.

"What?" Isabella asked in shock.

That's when Phineas realized what he just said. "S-Sorry," he told Isabella as he scratched his ear. "I was thinking about something dad once told his favorite companion."

"Hold on a minute," Isabella said. "You look like something from Candace's dreams. Are you-?"

"Yes Isabella," Candace interrupted. "That's Phineas, Ferb, and Perry the alien platypus."

"He does a lot of things," Phineas said, referring to Perry.

"Candace mentioned him once," Isabella replied. "She always talks about how the three of you travel throughout time and space. It sounds like a whole lot of fun-"

"Would you like to come?" Phineas bluntly asked. "No one will even know you're gone."

"Not so fast," Candace said. "As Isabella's legal guardian, it's my job to make sure she doesn't get hurt."

"There's always room in the TARDIS for one more person," Ferb offered. "It's actually bigger on the inside."

"Gyururururururu," Perry said, looking a bit impatient.

"Don't worry," Phineas told the alien platypus. "We're only inviting two people."

Inside the TARDIS, Ferb was working on the control panel.

"Here are a few things you need to know," Phineas told Isabella and Candace. "The TARDIS is a living being, so it has a mind of its own. We might end up somewhere that wasn't on the schedule. Plus, the rooms are occasionally rearranged, but Perry can help you out with that. He knows where everything is due to being part robot. Any questions?"

"Where's the bathroom?" Isabella asked.

"Here, here, and here," Ferb answered, pointing in three different directions."

"And now that everything's explained," Phineas said. "Ferb, throw that switch!"

And so, Phineas, Ferb, Perry, Isabella, and Candace began their big adventure together.