It was told by Heinz through his backstories that he had a terrible childhood in his native country Drusselstein that his parents caused. As it turns out, they did many horrible things to Heinz when he was a child such as:
- Being absent from his day of birth (though that leaves the question of how Heinz was born without too much sense)
- Forcing him to wear girl clothes following the birth of his younger brother Roger.
- Forcing him to become a lawn gnome after their real one was repossessed.
- Shutting off any contact with him for a long time after he refused to make a high dive out of fear.
- Briefly disowning him and letting him be raised by a family of ocelots.
- Favoring Roger over his skills in kickball while ignoring Heinz's skills in stacking cups (though it's only stated that Mrs. Doofenshmirtz favors Roger, as Mr. Doofenshmirtz's relationship with his younger son wasn't specified while he favored his dog whom he dubbed "Only Son").
- Tricking him into leaving for ship for America so that they can get rid of him.
So far, the only good things the Doofenshmirtzes did for their eldest son was giving him some toys (as some flashbacks depict Heinz playing with toys in his house), paying him a worth of allowance (though it was just a 3 cent coin) and, in Mr. Doofenshmirtz's case, telling Heinz the story of his ancestor Jekyll Doofenshmirtz (though it was actually to scare Heinz into bedwetting).
Due to this tragic childhood, Heinz went into a life of evil, eventually becoming an evil scientist and creating an evil business. It was also the cause of Heinz's annoying and eccentric personality as he had no one to rely on until high school. Despite this, Heinz tried to find his way into earning the love and respect of his parents, but ultimately failed due to their behavior; even Heinz's nemesis Perry the Platypus feels sorry for Heinz after seeing how very shallow Mr. and Mrs. Doofenshmirtz are over their behavior towards him. In spite of his tragic childhood, Heinz has no intention of repeating the same cycle of abuse towards his own daughter Vanessa as he intends to make her life happy regardless of his reputation as an evil scientist, a revelation that Vanessa accepts as she considers her father to be a better parent than her own grandparents.
It's unknown what happened to Mr. and Mrs. Doofenshmirtz following Heinz's retirement from evil, but it's likely that things are still the same, though it can be inferred that Heinz will no longer care about them because he has surely realized that they don't deserve his love and affection and that he's better off without them.
- Given to their neglectful and abusive behavior towards Heinz Doofenshmirtz (despite being played for laughs) and the fact that they received no comeuppance for it (the closest thing could be when Mr. Doofenshmirtz lost his garden gnome but that only worsened things for Heinz), Mr. and Mrs. Doofenshmirtz are considered to be two of the series' most hated characters by fans alongside Suzy Johnson.
- Mr. and Mrs. Doofenshmirtz can be considered The Heavy of the series (at least in Heinz's character arc), as their abuse and neglect towards Heinz is what caused him to become evil in first place, thus becoming the main antagonist of the Phineas and Ferb series.
- While not confirmed, it can be possible that Mr. and Mrs. Doofenshmirtz are divorced, as Mrs. Doofenshmirtz is seen to be living in Danville in "Thaddeus and Thor" while Mr. Doofshenmirtz is seen to still be living in Drusselstein in "Father's Day". It might be possible, however, that they still live together but that Mrs. Doofshenmirtz traveled to the USA for the Doofshenmirtz Family Reunion whereas Mr. Doofshenmirtz was unable to do so and that she was absent from the house when Heinz visited his father in the latter episode.
- It's unknown if there were a 2nd Dimension Mr. and Mrs. Doofenshmirtz as the 2nd Dimension Dr. Doofshenmirtz never mentioned either his parents or brother. However, if they existed too in the 2nd Dimension, it is likely that they were loving and caring parents to 2nd Heinz as his descent into villainy happened when he lost his toy train.
- By the time of the episode "Act Your Age", both Mr. and Mrs. Doofenshmirtz can be either deceased or very old as Heinz is likely around his early 60s.