"Bewegen Sie nicht!"
"Are you a man or a schnitzel!?"
He never payed attention to his son Heinz, so Heinz often felt left out and worthless. Mr. Doofenshmirtz and his wife even disowned Heinz at one point, leaving him to he raised by a pack of ocelots. ("The Chronicles of Meap")
At one point, Mr. Doofenshmirtz and his family hit lean times, and one fateful day the family was so poor that his beloved garden gnome was repossessed. As a replacement, he dressed Heinz as a garden gnome and forced him to be the family's lawn gnome all day and night without allowing him to move in the slightest for any reason even to eat or sleep. ("Lawn Gnome Beach Party of Terror") During one night, Heinz' only companion, Balloony flew off, but because of Mr. Doofenshmirtz's strict "no-moving" policy, Heinz had to remain still and could not retrieve him. ("The Chronicles of Meap")
Mr. Doofenshmirtz owned a Spiztenhound puppy which, according to him, was like the son he never had and named him Only Son. He won Only Son in a game of "Poke the Goozim With a Stick", which then grew up to become an award-winning show dog, bringing him fame and fortune. Even though this should have allowed the family to buy back the lawn gnome, Heinz was still forced to be the lawn gnome. This appears to be the source of Doofenshmirtz's fragile self-esteem ("Got Game?")
He once bought Heinz a toy train set, but never let him play with it, and played with it himself instead. ("Not Phineas and Ferb")
When his son Heinz was about 16, Mr. Doofenshmirtz and his wife tricked him into leaving for America by sending Heinz to go to the "Schtor", which turned out to be just a painting of a Schtor in front of a ship entrance, leaving Heinz on a ship bound for America, with Mr. and Mrs. Doofenshmirtz celebrating as their plan worked and the ship took off with their son. ("This Is Your Backstory")
He was among the special guests at Heinz' self-constructed "This is Your Life" show, but upon entering the stage, he only yelled "Bewegen Sie nicht!", just like when he made Heinz the family lawn gnome when Heinz was a child. ("This Is Your Backstory")
On Father's Day, Heinz decides to go back to Drusselstein to retrieve his father's repossessed lawn gnome and hopefully try to make amends with his father, who still lives in Heinz' childhood home in Drusselstein. However, when Heinz comes in with the lawn gnome, he trips on the rug and the gnome smashes to pieces. His father tells him that Roger gave him a bigger lawn gnome that is more impressive because it makes espresso. But his father decides it is the thought that counts. Heinz leaves disappointed, but after he leaves, his father sees the gnome with the serial number of the gnome that was repossessed so many years ago. Later, he is seen glueing the shattered gnome back together and telling the gnome not to move, just like he told Heinz to do in his youth. ("Father's Day")
Unlike his own children, Mr. Doofenshmirtz loved and cared for the family's pet dog Only Son, who brought the family much fame and fortune as an award-winning show dog.
Roger is the second son of Mr. Doofenshmirtz, though they have not been seen interacting with one another since their respective debuts. None-the-less, like his wife, the elder Doofenshmirtz still shows clear favoritism towards Roger, who seems to have a much better relationship with his father than his brother's relationship to him, though this is not saying much. Mr. Doofenshmirtz showed favoritism towards Roger, when he older son, when he made Heinz the lawn family gnome, and not Roger. It appears that Mr. Doofenshmirtz and Roger are on fairly good terms at least in the present, as Roger sent him a Gnome-shaped espresso machine that was taller than him as a Father's Day present.
Mr. Doofenshmirtz is one of the main driving forces behind Heinz's rather "evil" way of life. He "refused to show up" for Heinz's birth or attend any of his self-thrown birthday parties, denied him the basic rights of childhood, and even briefly disowned him.
However Heinz appears to generally wish to reconcile with his father and even considered using an inator to make him love him. ("Fun House") When he greeted his adult son for the first time on screen he showed apathy towards his son's "gift of rubble", however when Heinz left Mr. Doofenshmirtz noticed that the rubble contained the serial number DAEHM23 and deduced that the gift was actually his beloved Lawn Gnome. He has repaired the gnome but their relationship is still strained at best.
- Most of the words he says are in German. They are: "Bewegen Sie nicht!" ("Do not move!") in "Lawn Gnome Beach Party of Terror", "Nеіn!" ("No!") in "Not Phineas and Ferb", "Zu nah!" ("Too close!") and "Ich habe keinen Sohn." ("I don't have a son." or "I have no son.") in "Split Personality". The only words he has been heard speaking in English before "Father's Day" were "Are you a man or a schnitzel?!" in "Split Personality."
- In "This Is Your Backstory", it appears that he looks exactly the same since Heinz's childhood meaning that he looks the same now as he did when Heinz was a child. However, in "Father's Day" he is shown to be an old man with gray hair.
- The only childhood backstory of Heinz that his father has not made so much as a cameo in is the backstory when Heinz explains his past birthday troubles, where his father is absent from both his birth and later birthday parties.
- "Lawn Gnome Beach Party of Terror" (First appearance) (Appears in flashback(s))
- "Lawn Gnome Beach Party of Error!" (Spot the Diff episode) (Appears in flashback(s))
- "Got Game?" (Appears in flashback(s))
- "At the Car Wash" (Appears in flashback(s))
- "Phineas and Ferb Christmas Vacation!" (Pictured only)
- "Not Phineas and Ferb" (Appears in flashback(s))
- "Split Personality" (Appears in flashback(s))
- "Rollercoaster: The Musical!" (Appears in flashback(s)) (Cameo)
- "My Sweet Ride" (Appears in flashback(s))
- "This Is Your Backstory"
- "Father's Day"