I doubt Doof is related to Phineas & Candace because 1) they don't recognize each other like that whenever they meet and 2) His daughter Vanessa is around Candace's age.
While he is "evil", don't think Doof could cheat on his wife & certainly not long enough to be Phineas's dad. While he did get divorced, it's more likely that I'm Perry the Platypus than Doof is Candace & Phineas's dad.
Hmm i dunno, I felt like this may have been the start of him actually having some worthwhile enemies and story lol Not saying it's a masterpiece or anything but I'm enjoying it for what it is at least.
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