When comparing the show to the film series, therefore, it's quite easy to sort each of the main characters into one of the Hogwarts Houses. Whether it's Gryffindor, Hufflepuff, Ravenclaw, or Slytherin, each of these characters displays some of the traits necessary for the Sorting Hat to ultimately decide where they belong.
Phineas: Gryffindor
Phineas is the most charismatic of the two brothers and indeed a bit of a showman. He is brave and loyal to his friends, but also ready to stand up to them if need be. The fire audiences have seen in Phineas is certainly impressive and would allow him to fit into Gryffindor well.
While he certainly displays some Ravenclaw traits, including his curiosity, there are plenty of occasions where his chivalry and impressive feats have demonstrated why his heart is with the lion. There's no doubt that Phineas would do well in a Hogwarts Classroom.
Ferb: Ravenclaw
While Phineas might be the face of the group, Ferb is really the brain of the operation. He is a lot more reserved and quiet, but is always thinking of new inventions and continuously follows his own curiosity. He, therefore, fits into Ravenclaw incredibly well.
In his older years, he has showcased some impressive chivalry and built up a great deal of charm, especially in regards to his love interest Vanessa. However, he will always be known for his blueprints and schemes, with his logical thought processes sorting him into Ravenclaw.
Candace: Slytherin
The easily memed Candace is really perfect comic relief for the show. Her obsession with busting her brothers has gotten her into all sorts of silly situations and she is almost never victorious. Yet her determination and mad schemes definitely show off her Slytherin side.
All of her emotions are incredibly intense, whether it's her love for Jeremy or her need to get Phineas and Ferb in trouble. Her future demonstrates that she is very ambitious though and her relationships (such as her friendship with Stacy) showcase her Slytherin loyalty.
Linda: Gryffindor
It's well known by Phineas and Ferb fans that Linda is Phineas's biological mother and there are therefore a few similar traits between them asides from their red hair. While she contains the determination of Candace, her Slytherin daughter, she also has Phineas's loyalty and bravery.
What's more, there's a firey side to Linda and she's always ready to protect her family at any cost. She loves putting on a show, with a past as a one-hit-wonder, which also showcases some of the attention-seeking traits of the Gryffindor House.
Lawrence: Hufflepuff
Lawrence is Ferb's biological father, although the green-haired brother actually shares more traits with Phineas than he does his own dad. Lawrence isn't quite as intelligent as Ferb, although he does share the same curiosity and love of the past.
He is ultimately a really kind and caring father though and demonstrates plenty of Hufflepuff characteristics. Even his bid to try and show his wife how much he loves her might have been a little bit disastrous, but the effort that was there was a clear sign of his big heart.
Perry The Platypus: Ravenclaw
It's difficult to imagine Perry The Platypus on the trip to Hogwarts (outside of being a wizarding pet that is) but Perry demonstrates both Gryffindor and Ravenclaw traits. If the Sorting Hat had to decide though then he would probably pick the latter of the two options.
Perry is clearly brave and loyal to his family, which are both Gryffindor characteristics, but he also deals with situations very logically. Sarcastic and quick thinking, his adaptability and ability to prepare for any given situation, are all signs of his Ravenclaw nature.
Dr. Doofenshmirtz: Slytherin
Dr. Doofenshmirtz is supposedly evil but that might not actually be true. From the movies to the TV show, Dr. Doof has demonstrated that he does actually have a kind heart and even has a great deal of respect for Perry The Platypus. That doesn't stop his evil schemes though.
His ambition, dark side, and intelligence all suggest that he is actually a Slytherin. However, if Doof perhaps didn't have such a horrible childhood then maybe his House would have actually been something quite different, considering he has a great capacity to feel affection for others.
Isabella: Gryffindor
Phineas and Isabella are really well matched for each other partially because they are actually in the same House! A natural leader, Isabella is well known as the head of the Fireside Girls, who are always prepared for any given situation. She shows great charisma in this role too.
What's more, she is incredibly brave, fearlessly following Phineas and Ferb wherever their crazy adventures might take them. She's very loyal to her friends and will stand up for both them and herself when she needs to. Isabella is certainly one of the most recognizably Gryffindor characters of the show.
Baljeet: Ravenclaw
Baljeet is maybe one of the most logical and quick-thinking characters in Phineas And Ferb. He might be a little awkward, but what he lacks in social skills he more than makes up for with his impressive mind. Baljeet is also a stickler for the rules.
As the show evolves he learns to stand up for himself against bullies like Buford, but can still see the humanity inside of him. He might not be brave enough to be a Gryffindor, or cunning enough to be a Slytherin, but Baljeet definitely fits perfectly into Ravenclaw.
Buford: Slytherin
Buford might have shown the greatest amount of progression in the series; as well as the spin-off show he has starred in. The character began life as the neighborhood bully, but after becoming a significant member of the group, continued to develop in his personality.
He might still be a little brutish and not overly intelligent, but his confidence and self-worth are great to see. His earlier characteristics during his bully days definitely matched him into Slytherin House, but his later evolution shows off some of the better Slytherin traits.