Phineas Flynn is one of the two titular main protagonists alongside his stepbrother Ferb Fletcher of the Disney Channel Original Series, Phineas and Ferb. He is one of three children of the Flynn-Fletcher family, with a disapproving older sister Candace and Ferb. He shares a strong bond with the family pet, a platypus they named Perry, but remains unaware of his vague double life as a covert agent and is usually the one who realizes he is missing and wonders where he is.
An incurable optimist, Phineas constantly looks on the brighter side of things. He is also extremely smart, creative, and persistent, allowing him to be able to endeavor in immensely large projects and activities with the help of his less-talkative stepbrother Ferb, and usually with many other neighborhood children. His hospitality is a driving force behind many of his plans. The series concerns Phineas' attempts to avoid constant boredom by finding something new to do every day during summer vacation. The activities they devise usually involve outlandish contraptions, including roller coasters, haunted houses, and roller rinks, which Phineas designs and Ferb builds. He is also one of the three titular characters of the Phineas and Ferb/Milo Murphy's Law Universe the other two being Ferb Fletcher, his step brother, and Milo Murphy, his friend.