Heinz Doofenshmirtz sometimes tells backstories about his childhood or recent events that have happened earlier to Perry. They reveal the events that motivated him to pursue a scheme or build an Inator, and thus become an evil scientist.
The Doofenshmirtz family lived in Gimmelshtump, and when they came across lean times, their beloved lawn gnome was repossessed. Since it was necessary to protect the zatzenfruit garden against "witches, spells and wood trolls", his father dressed Heinz up as a gnome and forced him to stand watch for hours at a time during the day and night. Any time Heinz tried to move, such as when friends came by to play "Kick the Schtumpel", to eat Doonkleberries or to wave at his neighbor Kenny, his father was right there, yelling at him "Bewegen Sie nicht!"("Don't move!") .
At Heinz's birth, neither of his parents "showed up". At five years old, Heinz threw his own birthday party at Gunther's Goat Cheese's. His "closest friends" were there; two wolf puppets, Betty the pig, a rat and the lice twins Olga and Chicago Joe. A man wearing a goat costume walked up to the table and greeted Heinz. He placed the Doonkelberry cake on the table and left. The restaurant manager then shouted out to Heinz "Hey kid, lock up when you're done, 'kay!". At night, Heinz ran home with the cake in hands, and was attacked by the Doonkelberry bats, who likes eating Doonkelberry cake.
Later, in "This Is Your Backstory", this was slightly revised that after ten seconds, the cake was repossessed after Heinz found out that there was a two-person minimum.
When Heinz was younger, he performed magic tricks for the local kids. Heinz performed the pull-the-rabbit-out-of-the-hat trick, and instead of pulling out his rabbit companion, Bobo, he pulled out a skunk, which sprayed him. Next, he performed a card trick. A girl volunteered to pick one of Heinz's cards, while he blindfolded himself. When Heinz uncovered his blindfold, he appeared to be holding the same skunk, who sprayed him again. Yet again, another trick went wrong, and while Heinz shouted for someone to help him get out of some chains, the skunk came along and sprayed him once more.
Heinz watched his father come home with a brand new puppy that he won him in a game of "Poke the Goozim With a Stick". The puppy was named "Only Son", because it was like the son that Heinz's father never had. Only Son became a famous dog, which brought fame and fortune to the Doofenshmirtz family. After this, Heinz was still forced to be the lawn gnome.
After trapping Perry in sticky flypaper, Doofenshmirtz tells him a story about a moment from his childhood when a bully named Boris would always kick sand into his face. Everywhere he went, sand was kicked into his face. Due to these events, he became paranoid and felt that sand would be kicked at him at any time. Except at the beach when he was expecting it, but didn't. Even when that happened, he was still scared of it.
Perry arrives at Doofenshmirtz's space station, shaped like a giant robot with huge hands and nothing below the waist. He gets sucked inside the robot and frozen in an ice cube tray by Doofenshmirtz. Using a crane on a track, Doofenshmirtz shows Perry the Platypus his station while telling him a story from his teen years. It seems Doofenshmirtz was very adept at hand shadows, or shadow puppets. He found it great fun for entertaining people and meeting girls (Fräuleins). Unfortunately Heinz's fun was ruined when a new boy arrived by the name of Hans. His puppetry wasn't very good, but that didn't stop him from taking away the girl that Heinz was trying to win over. He never did a shadow puppet again.
When Doofenshmirtz was young, he built his first inator, but it lost to a kid with a baking soda volcano. The next year, Doofenshmirtz made an even bigger inator, but lost again to another kid with a baking soda volcano. When he got older, he was into poetry: "The movies are gray/The TV is black/The horses are running/Please bring me some food." Yet, he still lost to another baking soda volcano.
Later in "This Is Your Backstory", Heinz said that the volcano's poetry lacked substext.
Doofenshmirtz recalls his days as a bratwurst street vendor, which he described as being less evil than his current occupation. Despite the fact that bratwursts had "superior workmanship, finer meats and exotic spices", street vendors that sold hot dogs did much better than bratwurst vendors. At the present time, almost no one (other than Heinz himself) remembers that street vendors once sold bratwursts. Heinz attributes this to hot dog vendors "having it all": chrome-plated carts, endorsement deals and fancy blimps.
After two young boys walk by and make a joke about selling bratwursts being a telling sign that a person is lame, Heinz vowed that he would get revenge against the hot dog vendors, introducing his Hot Dog Vendor Revenge-inator in the process.
Doofenshmirtz used to love a girl named Elizabeth who loved whales, and since he loved her so much, he invented a whale-translator-inator. The whale told the girl that she should dump Doofenshmirtz and go out with him.
Heinz's mother was expecting a baby girl, and knitted hundreds of dresses. The baby turned out to be a boy, Roger, and Heinz was forced to wear the dresses for a year and mocked by his classmates for it.
Doofenshmirtz tells of the time when the Fireside Girls (in this case, Katie and Gretchen) came to his apartment after hours to sell him cupcakes or raffle tickets, but he forgot to close the curtains to his window and they could see him still, thus causing the creation of his Invisabile-inator to make them all disappear.
Doofenshmirtz tells Perry that when he was a boy, the smell of pork emanating from him was so bad that nobody would come near him. However, one day, the carnival came to town, working at the dunk tank (but not as the dunkee but rather the object to be thrown at the target), he got a balloon, painted a face on it, and named it Balloony. When Heinz was dressed as the lawn gnome one night, Balloony floated away. Heinz tried to reach out to it, but Heinz's father shouted out to him to stand still. Heinz, upset, watched Balloony float away into the night sky.
Doofenshmirtz tells about how he buying a new home following the divorce from his ex-wife Charlene, and was shown a skyscraper that would become DE Inc. headquarters complete with a view of the ocean. The one problem was that the building was located near the Danville Lighthouse, with the boats blowing their foghorns all night long, and as a result Heinz was unable to get any sleep.
Doofenshmirtz recounts the time he was forced by his doctor to go on a low-carb diet, and tries to lose those last ten pounds when Milly and Katie from the Fireside Girls were at his door and tried to sell their cupcakes, and is weakened into doing this, so he makes a Metal Destructinator to turn metal into broccoli and destroy the bridge to their cupcake baking factory.
Doofenshmirtz tells his story about people laughing at him the day before because a mime was mocking him. Doofenshmirtz then shows Perry his 'Mime-inator', and states that he made this machine to trap every mime in the Tri-State Area inside an invisible box.
On a gerry-rigged rocket powered jet skiff with Perry aboard, Doofenshmirtz tells him about one of his first dates. It was with Linda Flynn-Fletcher at a drive-in theater to watch a movie. Linda says that she would like to be a pop star one day. Doofenshmirtz sarcastically replies that he will take over the world, and she suggests that he should start small and try to take over the Tri-State Area. Doofenshmirtz says it's unlikely but he'll try. He then brings out a machine to make the movie's sound fifth dimensional and attaches it to their car. Unfortunately, the machine makes the cinema screen explode and blast off into the sky.
During his childhood, Heinz's parents expected him to perform a high-dive as a rite of manhood. However, Doofenshmirtz had been too afraid to dive and was forever scorned as a "schnitzel". Because he did not jump into the pool as he was too scared, he shamed his family, and his father hated him even more.
Heinz welcomes Perry to his space station, which he echos - but one of them is broke. Perry gets on a chair that can from under him for Heinz to do a presentation. Ten years ago, Heinz had been backpacking around Europe, when he came across some Canadian college students. Dillion was the most popular one of them, but Heinz was the oldest.
Finishing the story, he is never welcome in Albania ever again, and had ended up in Italy and went to the Leaning Tower of Pisa, but they didn't make pizza there. Doofenshmirtz complains that it had pizza in the name, and since they were out of it, he didn't get any pizza.
While a boy in Gimmelshtump, Heinz was walking through the "claw machine district" when he found a claw machine with a teddy bear inside instead of the usual rocks. He used his entire year's worth of allowance (a three cent coin) and won the bear. He gave it to his mother as a trophy, who immediately gave it to his brother Roger. Roger took a big red marker and wrote his name on the bear and his mother's blouse, effectively claiming both as his own and thus shutting Heinz out of the family dynamic.
Doofenshmirtz tells Perry, trapped in a pickle, that a few days ago, he went to Tony's Delicatessen to order a chicken soup but he argued with the owner over a fly (or is a raisin?) that he found in the soup- he even took the specimen to an etymologist.
When Doofenshmirtz went on a camping trip, he was attacked by bees. Heinz was allergic to bee stings, making him deeply afraid, and they chased him down a hill. He apparently got a fire hydrant stuck in his leg, but doctors couldn't remove it because it was too close to an artery.
Perry breaks into a window of Doofenshmirtz Evil Incorporated and is immediately tied up to a luggage carrier. Doofenshmirtz wheels him to his hovercraft and shows him his Stain-inator. He explains his back-story and plan on the way. When he was a youth in Gimmelshtump he yearned for a career in fine arts. He loved painting, though found his muse somewhat inaccessible. One day as he was about to give up he gained inspiration and stayed up for three days painting his masterpiece. However, his brother Roger accidentally spilt sloppy Joe and many other foods and drinks on it. Doofenshmirtz made a solemn vow that Roger would someday pay for what he did, and had his vow notarized.
When he was about to click on bid now for an inator, a popup ad got on the bid now button, he was forced to remember how he once did an ad with a wombat that was too close to his face to pay for one of his early inators. He ultimately decided to make his own popup ads to make millions.
Perry enters Doofenshmirtz's apartment to find that Heinz has chained himself up and explains that a few days ago, he declared war on grass, so he got himself a cow, the natural predator of grass. However, the cow was too slow, so Doofenshmirtz invented the Mind-Transfer-Inator to motivate the cow to work faster. Instead, Doofenshmirtz developed gaps in his memory, a strange craving to lick salt, found himself watching the nightly farm report as well as The Pasture Channel way more than usual, and because of this, he suspects that he is no longer human, which is why he needs to tie himself up. All of a sudden, as a full moon comes out, he transforms into a were-cow, and breaks the restraints.
Heinz tells Perry about pretzels and explains back in Drusselstein as a child that he used to be an intern worker at Master Drakkenblad's Pretzel Palace and that no matter how many times he tried to make a pretzel he always made a knot, thusly was kicked out and deemed unworthy and since then he hated pretzels.
In this episode, Doofenshmirtz explains that a pizzeria has a "37 minutes, or it's free" policy. The pizza man then knocks at the door, as Doofenshmirtz slowly glides his feet along the floor on his way to the door, checking his watch while doing so. At the door, the pizza man has him pay anyway. Seeking revenge, he decides to set up explosive pizza dough in his shop. However, Doofenshmirtz's plan fails after it has been turned it into an exploding pizza special.
An original backstory was told at the start of part two of this clip show. At age 16, Doofenshmirtz went to the store (spelled "Scthor") but was tricked into going onto a boat away from Drusselstein by his parents. He swabbed the deck to pass the time, and "was headed to a land of opportunity where golden opportunity awaited...but ended up in America instead" where upon departing, a giant crate was dropped on him.
In unveiling a replica of a Drusselsteinian car, Heinz explains that he had an uncle who had a similar ride that was brought out on cruising nights in Gimmelshtump along with other vehicles that were rebuilt from takeovers by outside forces.
Doofenshmirtz-2's "evil" backstory is losing his toy train, causing him to become an evil dictator. He later finds his toy train after attempting to smash Phineas, Ferb and Agent P. Also, Doofenshmitz mentions some of his previous backstories.