Major Francis Monogram is a supporting character of Phineas and Ferb. He is Perry's commanding officer, and gives him his mission in each episode. Helping him transmit the messages is his intern Carl. Since the third season, he doesn't hate being called Francis.
Vote which fictional character would naturally fit in-universe with a big-named franchise! No time-travel, no interdimensional crap, no "Pooh's Adventures", they would just exist in-universe.
