Ferb FletcherFerb Fletcher - Ferb is Phineas's intelligent but laconic stepbrother. Ferb is a very quiet boy, but he is not exactly shy. He is incredibly brilliant and has a great sense of mechanics & electronics. He almost single-handedly built a roller-coaster and giant track, a real radio-controlled race car, several arenas and stadiums, a space ray (which was supposed to be an ice cream maker but the plans got confused), a monster truck, a shrinking submarine, and a time machine. He doesn't say much, but is always willing to help Phineas in his incredible plans, no matter what are the circumstances. Whenever the usually-reticent Ferb talks, he speaks in a very sophisticated English accent, thus confirming that he and his father are of British origin. Ferb is talented at changing his voice. When he sings, usually uses a deep, Afro-American voice instead. He is also seen as having a knack for roller-skating. In the episode "I Scream, You Scream," he is shown to have a crush on Vanessa Doofenshmirtz, husky-voiced daughter of Dr. Heinz Doofenshmirtz. Like Phineas, Ferb is also talented and can play a large variety of instruments, including the Jamaican drums.

Candace FlynnCandace Flynn - Candace is a 15-year-old teenage girl. She is always aware of the boys' plans. She is generally a spoil-sport and always attempts to get the boys in trouble with their mom. But when she finally gets her mother's attention to see what they are doing they always look perfectly innocent and normal on account of the unaccounted-doings of Perry the Platypus and Dr. Heinz Doofenshmirtz. Candace nurtures a permanent crush on Jeremy. She often uses her cell phone and acts much like a stereotypical teenager when not trying to stop her brothers' antics. In a sense, she is the exact opposite of her brothers, being terribly afraid of heights and easily getting sick or dizzy. She has a "Panic Room" in their garden to hide in when she freaks out on account of her brothers’ tricks. While Candace is constantly angry at her brothers, there are indications that underneath she loves them. Candace is good at singing and can play a number of instruments, all of which begin with the letter "B".

Perry the PlatypusPerry the Platypus – Perry is the boys' pet platypus, who lives a parallel life as a secret agent. He has a lair under the Flynn-Fletcher's house that can be entered through various passages around the house. His nemesis is the evil scientist Dr. Heinz Doofenshmirtz, and Perry always accomplishes his missions to stop the doctor's evil designs and plans. A running theme in the show is that his missions end up covering up evidence of Phineas and Ferb's activities by accident, therefore the boys’ mom never finds out about their schemes and antics. While Perry never says anything throughout the show, he can make a growling noise or teeth chattering that he uses at random times. Perry works for his boss “Monogram’- who appears to be a stern, hard-boiled spy master. Perry is equipped with many hi-tec gadgets and instruments, including whistles that call certain animals, a grappling hooked gun, a parachute, several guns, a pocket helicopter, a jet-pack etc. He also can drive a scooter and has his own flying car and jet pack. Perry has his own theme song called "Perry the Platypus" which first appeared in the ending of the episode "Rollercoaster." In "Ready for the Bettys", the boys stumble on to Perry’s headquarters and his missions by accident, but they do not discover his secret identity. This is evident since after this episode, they never mention again the existence of the secret hideout. Usually, whenever Phineas says, "Where's Perry?", the platypus changes from pet into a secret agent and starts his mission. At the end of the mission he returns to his normal identity at which time Phineas says, "There you are, Perry." The most witty recurring gag of the show is the oft-repeated remark about Perry saying “Perry is a platypus and platypuses like Perry don't do much”. This remark looks extremely counter-factual and hilarious in view of Perry’s incredible spy adventures involving Dr. Doofus.

Dr. Heinz Doofenshmirtz alias Dr. Doofus - He is a mad scientist, who serves as the comic relief. Doofus’s ultimate plight leads the viewers to empathize with him. He is the head of his own single-person company, "Doofenshmirtz Evil Incorporated". His lair appears to be a standard major corporation, and even has its own company's theme song. All his evil but ridiculous plans tend to be thwarted by Perry the Platypus. The Doctor has turned evil because of his unhappy, unprovided and sad childhood in an almost unknown European town named "Giveupstuppen," where his family were poor farmers. Coming from this background, presently he attempts to wreak havoc across "the entire tri-state area," but it is unknown how he became a corporate billionaire or why he seeks revenge in the United State of America, instead of his own country. He is divorced and his ex-wife, Charlene, actually pays him alimony. He has a teenage daughter named Vanessa who is less-than-thrilled with him or his schemes. His eldest brother Roger -- and the favorite of their mother -- is a respected politician in Danville and holds the mayoral post. Doofus is not really a doctor as pointed out by his daughter, as his Doctorate Degree has a $15 price tag on it. He faked his diploma because he thought he couldn't be head of a company without it. Doofenshmirtz seems to have an active love life, since in "I, Brobot," he has relationship problems with his "new" girlfriend, and leaves a ton of pathetic messages on her answering machine. In "Get That Big Foot Outta My Face!," he has a date with a woman he met online, but Perry gets caught in the middle of it and ends up stealing all of the attention away from Doofenshmirtz. In the same episode, he mentions that wasn't his worst date, because there was one who tried to stab him with a fork sometime ago. He also has the weird habit of adding "-inator" at the end of most of his evil invention's names. But the weirdest of his habits is the building-in of the un-do or self-destruct button in all his inventions, which Perry eventually finds and defeats Dr. Doofus.

Isabella Garcia-ShapiroIsabella Garcia-Shapiro - Best friend of Phineas and Ferb. She's also the leader of the local Fireside Scout Girls troop. She can variate her voice as Ferb can, and often assists the boys in their plans, enlisting the whole troop of girls in the process (often to obtain new badges or other credits related to the scouts.). She is also a big fan of the boys and their plots, particularly Phineas, whom she has a crush on. She always enters into the scene with the coy remark, “Phineas, What’s you doin?”. However, it is unclear whether or not if Phineas is aware of her crush and may likely be avoiding that. While Candace makes any possible (and ridiculous) effort to be the focus of Jeremy's attention, Isabella makes no other efforts to get Phineas’ attention except help him in the organization of his schemes. She has a pet chihuahua named Pinky who is prone to spazz out. A curious detail to note, it is despite the fact she's the leader of the Scout troop, she rarely wears uniform even when commanding the troop.

Linda Flynn - Mother to Phineas and Candace, stepmother to Ferb. She is married to Lawrence Fletcher, but she seems not to use his last name as most other characters called her "Ms. Flynn". Linda is portrayed as a regular American mother, although she plays in a free form jazz band with Isabella and Jeremy's mothers, and was once a one hit wonder pop star under the name 'Lindana' in the 80's. She is generally busy or trying to relax when her daughter tries to get her to see that the boys are up to some crazy plan. Linda seems to think Candace is crazy and needs professional help. When the boys reveal their schemes and accomplishments she thinks they have an "overactive" yet "adorable" imagination. She can play the keyboard, the triangle, and the guitar. Her favorite band is Love Handel. She has her hair styled by one of the band's former members.

Lawrence Fletcher - Lawrence is an archaeologist from the United Kingdom. He keeps his treasured memories in a toolbox. His anniversary with Linda Flynn is June 15th. It is not clear if he is or not aware of the kids schemes. In at least two different episodes, he agrees to follow Phineas instructions and even forces Candace to cooperate. In the episode "It's a Mud, Mud, Mud, Mud World" he convinces her to participate in a demolition derby organized by Phineas. He doesn't says a single word about the large battle arena constructed on his own backyard for the race, and encourages Candace to drive one of the monster trucks, with him as a co-pilot. In "Dude, We're Getting The Band Back Together!" he thanks Phineas for organizing a massive concert on his house for his wedding anniversary, and in "Mom's birthday" he participates in a live web broadcast. In other episodes, he seems to be completely ignorant of any unusual behavior. Isabella has only once called him "Mr. Flynn".

Vanessa Doofenshmirtz Vanessa Doofenshmirtz - Dr. Doofenshmirtz's 16-year old teenage daughter. She is very sarcastic and mild mannered. Her dad and mom are divorced, yet her mother still has a good relationship with him. Vanessa is aware that he is an evil scientist and knows his father's enemy, Perry The Platypus. Her character's relation to Dr. Doofenshmirtz is like that of Candance's relation to Phineas and Ferb, as they both want to show their mothers what they are up to. A curious detail to note about her, it's that Perry and Vanessa seems to be completely invisible to each other, despite the fact that Dr. Doofenshmirtz constantly introduces her as his "evil assistant", though for Vanessa's sweet 16 party, Perry outwits Dr. Doofenshmirtz and accidentally improves Vanessa's party, in which Vanessa calls as Perry jets off, "thank you, Perry the Platypus!". Vanessa does not care Perry's presence in any way. She doesn't hurt him, but doesn't help him either, even when she has the opportunity she simply turns away instead. In return, most of the time Perry simply ignores her. She appears to be part of a Goth group and is dating a boy named Johnny. By coincidence, Candace often crashes, lands, yells or even travels next to Vanessa, but have only met once.

Jeremy Johnson Jeremy Johnson - Jeremy is the love interest of Candace. Whenever activities are going on in the Fletcher-Flynn house, he goes to visit just to enjoy the activity. For several incredible coincidences, whenever Candace moves from one location to another, he gets a new job near her, so he can always be around to witness Candace worry. In an interview with Mitchel Musso, the artist who does Jeremy's voice in the English version of the show, he revealed that Jeremy returns Candace's feelings for him, but in the series the only hints about it are his constant presence around her and a few minimal details that manifest a personal interest in Candace.

Major Monogram Major Monogram - He is Perry the Platypus's boss, who always gives him missions to stop Dr. Heinz Doofenshmirtz's endless reign of terror upon the Tri-state area. Major Monogram usually appears on a giant screen giving Perry instructions for his next mission. A curious thing to note is that both Monogram and Doofenshmirtz often mentions personal details about each other. The doctor even asks for Monogram's budgets, aides, health and sends him personal letters to inform him about his vacations, so Perry doesn't needs to bother at those times. All this suggests they have a close personal relation yet to be revealed (is that or Doofenshmirtz is really dumber than he looks like, since he informs his worst enemy of his personal activities). In the American version of the show, Major Monogram is voiced by Jeff "Swampy" Marsh who, in addition to voicing him, is one of the show creators and writers.

Karl the Intern - The person who operates the camera for Major Monogram's secret hideout. He is a bit forgetful and sometimes fails to focus the camera, so we can see Monogram is secretly doing something humiliating that he's not supposed to do, after which he immediately says "Karl, cut to close up". In an episode in particular, Karl points the camera to the floor by mistake, revealing Monogram is not wearing pants while giving instructions to Perry. Karl usually is in the back, out of sight, so most of the time you can only hear his voice while discussing or being scolded by Monogram, but from time to time, he makes brief appearances interrupting Monogram's speeches.

Stacy Hirano - Candace's very enthusiastic best friend. She rarely appears in person in the series, since most of the time she's talking by phone, but is usually in Candace's companion when something very exciting happens. She is one of the few persons who knows the truth about the boys. She witnessed the backyard beach, the roller coaster, the runway and the giant battle-tree-bots, but doesn't seems to be concerned about it. In fact, she usually convinces Candace to participate and enjoy the moment instead of trying to bust them. She is also telling Candace not to be so uptight about her dealing with her brothers. She figures prominently in "Tree to Get Ready" and "The Best Lazy Day Ever." Her mother is the doctor who performed the tonsillectomy on Isabella in "I Scream, You Scream."

The Fireside Girls Troop 46231 - They are the local girl scout group guided by Isabella. They like music and never have been seen without a smile on their faces. They usually count on Phineas and Ferb to help get their badges. Very little it's know about them though. They are mostly little helpers or supportive characters. In the episode "The Fast and the Phineas" Isabella thanks one of the girls calling her "Gretchen," but since she's talking with all at once, nobody can tell for sure who's Gretchen. Besides this, no other personal information is know about the troop.

Buford Van Stom - The neighborhood bully. At first looks very though and dangerous, but he is mostly an inoffensive but rude big boy. He likes tough stuff, but is afraid of the most trivial things, as shown in "Raging Bully," in which ice-cream falls on his pants and he screams. Since there's no real violence in the show among the kids, it is frequently mentioned that everybody is afraid of him, but he really does not hurt anyone onscreen. When he challenges Phineas to a physical confrontation, they thumb-wrestling instead, and at the end of the "fight" is Buford the one who proposes Phineas to be friends. He is constantly present as a good guy more than a bully, and for this reason receives frequent invitations from Phineas to join them in the fun. Buford owns a fish named Biff, after his mother.

Baljeet Patel - He is most likely from India's Punjab region, judging by his name and accent who is often portrayed as a weak and insecure kid, especially around Buford. For some reason, he usually ends teaming with him, which increases his constant nervous shakes. He's very smart, but most of his personality it is eclipsed by the extreme terror he feels when Buford stays around. A recurrent theme is his missing underpants. Even though Buford usually bullies him they usually end up working together as in "Greece Lightning."

Charlene Doofenshmirtz - Doofenshmirtz's ex-wife although she still has a good relationship with him thinking he is just a bit eccentric. She is in the same cooking class as Linda Flynn. Charlene is friends with Linda, and like her, seems to think that her daughter is crazy and needs professional help.

Grandma Betty Jo and Grandpa Clyde Flynn - They are the Flynn-Fletcher kids' maternal grandparents and they invite them with the neighborhood kids to a lake house every summer. Their names come from the creator "Swampy"'s great Aunt & Uncle. Though they are old, they sometimes like to get the best of the kids and often participate in their capers. Betty Jo has an identical twin sister. As a young woman, Betty was a roller derby champion whose chief rival was Jeremy's grandmother, Hildegard.

Hildegard Johnson - Jeremy's grandmother who was Betty Jo's chief rival in the roller derby. In a rematch they recruit their grandchildren to help them decide who was better.

Suzie Johnson - Jeremy's sister. She seems to be younger than Phineas and Ferb. She is obviously adept at devising machinery for the purpose but, unlike them, has a malevolent use in mind as seen in "Crack That Whip!".