Definitely not a true story. Phineas and Ferb is full of imaginative and creative elements that couldn't happen in real life. It's all about having fun and adventures in a made-up world.
When it comes to a 'phineas and candace lemon fanfic', it could also be a way for fans to express their own feelings about the characters. Some might write it to show their love for the show in a different way. It could be that the 'lemon' part is just a catchy way to make the fanfic stand out, or it could actually involve some sort of tangy or unexpected elements in the story.
The story of Phineas and Ferb is based on the adventures and creativity of two stepbrothers during their summer vacation. It's filled with wild inventions and fun escapades.
Phineas and Ferb is not based on real events. It's a creation of the show's writers and animators, full of creative and fantastical elements for entertainment.