Ally Wiggan' is the neighbor and one of the best friends of Phineas Flynn and Ferb Fletcher. She lives in Danville on Maple Drive, across from Phineas and Ferb's house, with her mother Jenna Wiggan. Isabella has a huge crush on Phineas (though he doesn’t seem to notice it. We see that this annoys her when her head “blows up” in France.) and spends most of her days participating or helping with his and Ferb’s projects. However she doesn’t tell Phineas. She also spends time trying to earn Fireside Girls patches and is also great friends with the members of her troop in the Fireside Girls. She is the female deuteragonist in Phineas and Ferb and is voiced by Icaly star Miranda Cosgrove. Allison Courtney Wiggan was born to a Jewish Mexican mother Jenna Smith-Wiggan and an her father Daniel Wiggan. At some point in her life, she met and became friends with Phineas Flynn and Ferb Fletcher. Her friendship with Phineas has somewhere along the way deepened into love and he is now her crush. Though it is unknown when, Isabella joined the Lil’ Sparks and later the Fireside Girls and worked her way up to become a troop leader.
Ally lives in Danville on Maple Drive with her mother in the house directly across the street from the Flynn-Fletcher House. She frequently participates in Phineas and Ferb’s projects, assisting in construction and maintaining order. Isabella owns and takes care of a chihuahua named Pinky, who she is unaware is a covert agent, like Perry. When on duty, Isabella works diligently upholding her position in the Fireside Girls and earning accomplishment patches. She is currently the captain of Fireside Girls Troop 46231. Its members are Gretchen, Milly, Ginger Hirano, Katie, Holly, and Adyson, with which she is considered not only a leader, but a great friend.
Ally is cheerful, fearless, quick thinking, sweet, beautiful, optimistic, caring, very helpful, and easy to get along with friend. She is very eager to help with any of Phineas and Ferb’s Big Ideas. When she participates with Phineas and Ferb in their endeavors, it’s either for the fun of it, her aspiration to earn accomplishment patches, or simply to be with Phineas. She comes over every day just to see him, as seen in the song What’cha Doin? (“Rollercoaster: The Musical!”) She is mostly optimistic, but she also cares for, and worries about people at certain times. Isabella is sympathetic and would aid people who are in need of it. This was demonstrated when she showed concern for Candace, who was too nervous to call Jeremy and ask him out (“Out to Launch”) and when she snapped Phineas and Ferb out of their hypnotic dullness (“Phineas and Ferb Interrupted”).
Being the Fireside Girls Troop Leader, Ally is a very capable vice leader. She is level-headed and responsible in the face of emergencies and dislikes being told what to do by anyone, with the exception of Phineas. However, she does gets jealous easily, and will get frustrated if someone that Phineas is giving a lot of attention to other than Isabella or when Phineas expressed seeing Meap as cute but not her (“That Sinking Feeling”, “The Chronicles of Meap”). As Isabella enjoys attention, she openly displays envy and discontent when she isn’t receiving any, like the time when her Lil’ Sparks men-tee, Melissa, showed Candace more attention and admiration than she did with her. (“We Call it Maze”) As sweet and adorable as Ally is, she gets angry fairly easily. One way her temper has been flared was when someone besides her or Phineas would use her catchphrase. In such a scenario, she would express being annoyed and would often confront the violator physically. One such time was when Suzy and Candace repeated her trademark catchphrase “What’cha Doin’?”
Ally has shown at least twice that she has a devious streak, taking advantage of a situation for her own benefit. These instances include her immediately jumping on Baljeet’s wager of squid versus Buford (“Voyage to the Bottom of Buford”). She also buys a play with the carny Shady Joe when a bowling ball Phineas and Ferb built knocks down all the pins (along with the stand), although Shady Joe is cheating by having the pins taped onto the shelf.