<P> Ferb Fletcher (voiced by Thomas Sangster) is a boy of few words, Phineas's green - haired, intelligent but laconic stepbrother from the United Kingdom and created by Phineas and Ferb co-founders Dan Povenmire and Jeff "Swampy" Marsh . He first appeared in the show's pilot episode, "Rollercoaster ." </P> <P> Ferb and his stepbrother Phineas Flynn spend their days during their summer vacation having fun . They are featured in every episode's A-Plot constructing large scale inventions or taking part in other outlandish activities . Ferb, an engineering genius, allows Phineas to do most of the talking for the pair and is described as "more of a man of action," by Phineas, which makes him more of a plot device than a developed character . Ferb is more likely to sing than speak, but most often has a one - liner in the episodes . Ferb is named after a friend of the show's creators who was an expert on tools and, at times, stayed rather silent . </P> <P> Candace Flynn (voiced by Ashley Tisdale) is Phineas's fifteen - year - old older sister and Ferb's stepsister . She first appeared in the pilot episode . Candace does not approve of the inventions her brothers create then she hates their creations, and in most episodes she attempts to "bust her brothers" by showing their mom . Her best friend is Stacy Hirano; Candace also has an obvious crush on Jeremy Johnson, but for a long time she was oblivious to the fact he liked her back . As a character, she has received a positive critical acclaim, having appeared in other media such as video games . </P> <P> Perry the Platypus (vocal effects by Dee Bradley Baker), a.k.a. Agent P, is Phineas and Ferb's pet platypus and first appeared along with a large portion of the main cast in the pilot episode "Rollercoaster ." Perry is featured as the star of the B - Plot for all but one episode of the series alongside his arch - nemesis Dr. Heinz Doofenshmirtz, at last he pretend to destroy their creations . He is a primarily silent character, with the only noises being the occasional rattling of his bill . </P>

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