So I've been watching Phineas and Ferb again and my headcanon is that Linda and all the adults do know about Phineas and Ferb and the things they build they're often so big and so many people are there, you'd have to be both blind and deaf to not know and even then I'm pretty sure blind and deaf people would know too. But at the same time.... what are you suppose to do? Ground them? Most of these things are built in the backyard anyway. Also, the things often disappear so it's like at least they clean uo after themselves (though it's actually doofenshmirtz who cleans up after them inadvertently.) Also, sure, building a roller coaster in your backyard is dangerous, but also they managed to make a functioning roller coaster. Like yes, you did something dangerous and that's bad, don't do that, but also that's impressive that you managed to do that.
And then there's things like the beach episode where its like, yeah, you maybe wouldn't let these kids go to the beach without adult supervision, but also technically they didn't go to the beach. They're still right there in the backyard, at home, and everyone else is technically just at Phineas and Ferb and Candace's house. Does this mean Linda is contributing to the mostly accidental gaslighting of Candace? Yes. But I also don't think she really knows how to address it. If she doesn't know, she never has to address it. So yeah, headcanon. There's no way she didn't see the burning remains of the roller coaster in the tree. At the very least. I know there's an episode where she does find out and send Phineas and Ferb away, but if I remember correctly that wasn't real, it was a dream Candace had or something. Also, Linda is the woman who went on a date with Doctor Doofenshmirtz and, when he talked about taking over the world, was like that's a cute goal but maybe start smaller, and Doofenshmirtz listened. So there is that. Of course its different when it's your children building potentially dangerous things but they usually come back unharmed, so...
Also I actually did for a while think Doofenshmirtz might be Phineas and Candadce's dad. But then I thought about it and was like, but Doofenshmirtz would never cheat, and I feel like he would've had to cheat to have at least Phineas. I don't know if Candace or Vanessa is older but I think they're around the same age. I just don't see it anymore.
However, I do feel like Doofenshmirtz would actually love Phineas and Ferb and would become like an uncle for them. He'd love their inventions, he'd be so supportive and they'd be like oh you built another fun inator? And Candace would try to bust them but one day, she'd just be down, she'd be upset, she's not in the mood to bust her brothers. And Doofenshmirtz, father to a teenage girl who he loves very much, immediately is like there's a sad teenage girl in my home, must cheer her up. Maybe Candace has had a fight with Stacey, or is having troubles with Jeremy, but for whatever reason, after some needling, Candace starts to vent to Doof. But instead if doing the thing people do where they only half listen, Doof is like "*gasp* no, she didn't. That's terrible. And then she called you dramatic?" Because Doofenshmirtz would be great to gossip to. He'd be so validating and so interested. He does manage to cheer Candace up just by listening and reacting correctly. And then he'd offer to make her and inator that will turn the other person's clothes into a potato sack or some other petty revenge. Wonderful.
Also Perry does go with Phineas and Ferb to Doofenshmirtz' and Doofenshmirtz does call Perry Perry the Platypus in both forms. But Perry the Platypus, Phineas and Ferb's pet, is still seen as completely different to Perry the Platypus, the secret agent. Because Doofenshmirtz is Doofenshmirtz.
But he'd be so supportive. He'd learn from Phineas and Ferb and teach them and help them. He'd call them his minions. He'd basically be like another father figure and would encourage their inventing because he remembers being their age and not having either of his parents' support in his inventing ventures. Also I think Buford would love the idea of hanging out with a mad scientist villain. And Baljeet would like having another person he could talk about science and school with who didn't seem bored, and who likes science just as much as him. Isabella would earn so many scout badges from bothe helping and stopping Doof.
