Chapter 1: An Unforgettable Day

Phineas and Ferb as always, are sitting beneath their tree in the backyard. "So Ferb, what is the plan for today." As Phineas said this, their mother walked into the backyard. "Hey mom, what's up?"

"You're father and I are going out for a while, your sister is out with Stacy and I need Ferb to come along with me. Remember Ferb, we have a few things to do for you today." Linda said waving Ferb over.

"That's right, Ferb is signed up to teach a dance class for today." Phineas slapped his forehead remembering.

"Right, so you're going to be alone for a while today unless you want to come with." Linda said giving her son a chance to come with.

"No, I'll just find something to do today without Ferb." Phineas said and watched as both Ferb and their mother left. He had expected to see Isabella to walk into the backyard at any moment but she didn't. "It's a lonely day today." Phineas got up off the ground and walked into the house. Phineas looked around the house and then said to no one in particular. "Hey, where's Perry?" Phineas asked and then sat down on the couch. Having the house completely quiet, Phineas heard a very quiet whistling sound behind him. Phineas turned around and looked at the picture frame. "What the?" Phineas asked himself as he looked behind the picture and was sucked into a small hole. Phineas screamed all the way down like he were on a rollercoaster.

Phineas soon landed on a chair and in front of him a giant screen. "Where am I?" Phineas questioned looking around. "Did Ferb build this as a club house and not tell me?" Phineas just kept asking himself questions until he tripped and hit a button on the control panel. Up on the screen popped up pictures of him, Ferb, and Perry in a Fedora. Soon flashes of memories came flooding back to him. "Holy cow, Perry is a secret agent, but how was I able to remember this if my memory was erased." That's when he remembered something else and he just had to leave Perry's agent room. When Phineas got back into the house, he took in a long deep breath. "I've got to go see Isabella, but first." Phineas said as he ran to the kitchen. "I know what I'm going to do today."

Isabella ran to the fireside girls HQ and went inside. "Ok girls, what patch are we going for today?"

"Why don't we just do what we do every day and go see what Phineas and Ferb are doing?" Adyson said.

"I would have but they had somewhere to be today and aren't home." Isabella said sadly.

"I thought it was just Ferb that had to be gone today but then again, those two go everywhere together." Gretchen said.

"That is exactly what I mean, if one of them is gone, they're both gone." Isabella said and then her phone rang. "It's Phineas." She said excitedly. "Hey Phineas, Whatcha Doin'? Isabella asked

"Isabella, come over to my house, I have a surprise for you." With that Phineas hung up.

Isabella went wide eyed, smiled widely, and then screamed and ran off. Once she reached her destination, she walked into the backyard and smiled to see a table with food and candles.

"Come sit down." Phineas said with a smile.

"What is all this Phineas?" Isabella said happily and then sat down at the table. 'This has got to be a dream, Phineas is here with me alone. No Ferb, inventions, or anything. If this is a dream, I don't want to wake up.' Isabella was so caught up in her thoughts, she hadn't even noticed Phineas come over to her and wrap his arms around her. Soon Phineas had started waving his hand in front of Isabella. "Oh what?" Isabella asked snapping out of her daze.

"Are you ok Isabella?" Isabella smiled and nodded. "Cool because I want to ask you something." Phineas paused for a moment and then continued. "How would you like to go see a movie tonight?" Isabella nodded excitedly. "Then I'll pick you up tonight."

"I have to go get ready, see you tonight Phineas." Isabella squealed as she ran off to get ready.

"Now to take care of a little something." Phineas quickly got to work on building a tiny camera with the help of Baljeet who he had immediately contacted. Soon Phineas had completed his task, grabbed a grappling hook and then grabbed his ninja suit and put it on. He made his way over to the building that looks like Ferb and made his way up to the balcony of the building and noticed Perry fighting with Doofenshmirtz. Quickly Phineas placed the tiny camera in the corner and aimed it so that everything could be seen.

'Now I can help Perry without anyone knowing.' Phineas thought to himself as he headed back home.

That night Ferb arrived back home and walked up to his brother. "So what did you do today?" Ferb asked.

"I've had a very productive day but hey brother of mine I have to go." With that, Phineas left to go pick up Isabella.

Ferb stretched and then headed upstairs to his room and when he walked into the bedroom, he noticed a note. Ferb picked up the note and some pictures fell out. Ferb picked up the pictures and looked at them and then read the note. 'Perry's a secret agent.' Ferb thought and then shrugged and fell asleep.

After the movie, Phineas walked Isabella home. "This has been an awesome day, thanks Phineas." Isabella smiled and was about to wave goodbye when Phineas grabbed a hold of her.

"Hold on Isabella, there is one last thing to do." Isabella raised an eyebrow in confusion. Before she could ask what the last thing to do was, Phineas kissed her on the cheek and then turned around and walked away, saying goodnight in the process of walking away.

Isabella smiled widely and slowly made her way inside the house holding onto her cheek.

Back home, Phineas walked into his room and found Ferb asleep. 'Night Ferb.' Phineas whispered as he changed into his pajamas.

'This is a day I don't ever want to forget.' Phineas and Isabella thought as the two of them fell asleep.

The End

A/N: Hope you enjoyed and please review.