The show 'Phineas and Ferb' is not based on a true story per se. It's more of an amalgamation of creative ideas. The characters and their adventures are products of the writers' and animators' imaginations. Although, it could be argued that some aspects, like the neighborhood setting and the typical family dynamics, might be inspired by real - life situations. But overall, it's a fictional world designed to bring joy and laughter to the audience.