All the informations are in the "Introduction".
"Hello, dear readers and watchers of this. As everyone is taking this kind of Challenge, I thought and I decided that I have to follow the trend too. My Challenge will have 250 Topics, and besides stories, I may add images to some of them. I'll make a comment before every mini-story and it will be written in this kind of letters. I may use some of OCs from the Fanon and I hope you won't mind. Of course, beware of some non-sense, I have a weird style to write. And I'll explain some stories before, as things like age may vary. And there will be different canons. I want to make it enjoyable. This is it."
"Did you break the fourth wall just to say that?" asked Candace, looking at the big hole from the wall.
"Yes, yes I did. Also, I wanted to warn you that I'm going to control all of you like some puppets."
It seems that almost everyone has "Love" in their first set, so do I. Some Stacebert, for your pleasure.
But what is love besides that huge black nerdy pair of glasses? Besides all the math formulas, all the chemistry and biology notes, besides all the ninja stuff? How is it to image her in your mind, holding her hand, seeing her in blur, in slow motion, with flowers around? But how is it when you're the type of person for who the logic has never failed? Feeling the shiver on the back when she's around and the happiness wants to burst out. When the whole world fades, and there's nobody left, but her.
"Brother, are you alright?" said Irving, shaking his blonde sibling.
"Yes, yes I am, annoying little brother. I'm just meditating about the things..." answered Albert, staring at the Japanese girl that just waved at him.
In this story, Candace is old. That's the only detail you need.
Candace stared at the window and saw the backyard of her lovely house. Outside, two young boys were playing with some mechanical bricks. They were both 5.
"It reminds me so much of something..." she whispered to herself. "Phineas and Ferb used to be that creative at their age. They look like my brothers, they act like my brothers, they build like my brothers... I wish I could see them again doing that. But I guess, these two little gifts will take their place soon, for the annoyance of their sister."
She continued to look at the two boys. They were Amanda's children, her grandchildren.
Can You Hear Me?
Mara looked in her back, seeing the three boys working at that project. Phineas was Isabella's, but Ferb and Eric were just for her. Both of them. A separate crush for each other, turning on and off. She felt like she was trapped in a triangle and she didn't know how to break it.
In her face, a portal opened. A girl, just like her, came from it.
"Oh, hello, me from other dimension!" Alt. Goth said to her.
"...Hello, I guess." Mara replied.
"Okay, so my Phin opened this portal again. Well, at least I can see what have you got here..." she told to her alternate self.
"Wait... Your Phin?" Goth looked surprised.
"Yup. Long story. He's cute. So is his brother. And I can't make my mind, so I'll like both of them before I'll decide. So, where's your Phin? Maybe he's cuter here." Alt. Mara continued chatting.
"Ummm..." she muttered. "He's in the backyard."
"Okay, thanks!" the alternate responded.
Goth felt like facepalming herself.
"Call me if you are alive after Isabella will see you!" she yelled to Alt. Goth, that made her way to the backyard.
"It's done!" Phineas said cheerfully, looking at the hair-dryer-lookalike thing in his hands. "Let's test it before we show it to Isabella."
The device that he was holding could make a different dress at every zap. The red-haired child stared at it for a few seconds and then, he moved his gaze to his brother.
"No, no, no. Let's test it on Jessie. Or Perry." Ferb answered, being sure of his sibling's intentions.
"Are you kidding me? I don't want to sign my death deed by dressing Jessie with this. And Perry wouldn't be pleased." he replied.
Perry chattered loudly, having a "Deja vu" experience, and remembering that blue ball gown that he got from Doofenshmirtz.
"See? He doesn't want. It will last only one second." Phineas explained, pushing a button.
Ferb didn't have any second to react, as he woke up wearing a pink long dress with matching hat and gloves. His brother started giggling, but it turned out in a loudly laugh. The next reaction of the red-headed child was to take the phone and make a photo.
Phineas' laugh became loudly again, as he showed the photo to his brother.
"When you'll have a girlfriend, I'm sure that she'll be glad to add this on the family album. But for now, I know a certain Flynn-Fletcher family that will love to see it." he exclaimed laughing.
"You wouldn't..." the British child replied.
"Why not?" inquired Phineas, running from the room, with Ferb on his steps. The chase wasn't so long, as Ferb felt on the floor.
"Come here... you little..." he tried to yell back to his brother, but he didn't listen. He was screaming to his mum, dad and sisters, laughing.
Ferb raised one leg and looked at the shoe on it.
"At least, I've got matching shoes..."
"Don't lose your pen." Candace said to Stacy.
"Candace, we weren't ever talking about pens. Why shouldn't I lose my pen?" Stacy replied to Candace.
"Well, if you lose your pen, then you'll have no pen. Without a pen, there will be no notes. Without notes, you won't study. Without studing, you will fail. If you fail, you'll have no diploma. Without a diploma, you won't get a job. Without a job, you'll have no money. No money, no food. No food means that you'll get skinny. If you get skinny, you'll be ugly. If you are ugly, then you won't be loved. No love, no marriage. No marriage, no children. Without children, you'll be alone. Alone means depression. Depression means sickness. And then death." the other teen answered.
"Umm... Why don't you buy a new pen then?" the Japanese teen responded.
What Could Have Been
Both Phineas and Linda are older here. Based on the "Phineas and Ferb's Quantum Boogaloo" events.
"I'm so proud of you!" Linda squealed through the phone.
"Thanks, Mum." her son answered.
"You really don't know how proud I am of you, don't you? I can't wait to see you. How is it there? When are you coming home?" she asked.
"Haha, don't worry Mum, I know. Well, I'm coming in few days. And it's amazing here. I'm going to tell you every detail when I'll come home." Phineas replied to his mother.
"Of course you're going to tell me every detail, I'm sure you have a lot to say! You won a "Marcel Benoist Prize*"! From now, your name is going to be at those TV shows with questions! It's going to be like: <<Who won the Marcel Benoist Prize?>> And the answer will be: Phineas Flynn, for sure!" she continued to chirp happily.
Phineas couldn't see his mother, but he imaged her swinging her hands in the air, like his name was appearing there. He giggled softly.
"Mum, there are a lot of people that won this prize in the past." the redhead said.
"But nobody was like you!" she defeated.
"Of course there were, Mum. They were even better." Phineas responded, but he knew his mother wouldn't give up. "Anyway, I talked with Ferb. He told me that he needs some antiques from your shop."
"I will send some to him. And don't forget, I'm proud of you!"
*The "Marcel Benoist Prize" is an award given in science. Because in the "Phineas and Ferb's Quantum Boogaloo", Phineas wasn't in Sweden, it wasn't probably to receive a Nobel prize. I'm thanking the Canon Wiki for sharing this information.