Agent E is a bald eagle who works for the O.W.C.A.. Her base is supposedly located near where Phineas's Grandparents live, as this is where her "nest" was located. She made her début in the episode "The Ballad of Badbeard".
Agent E came soaring down after Agent P is unable to open up one of the secret passageways to his lair in the area. She then took Agent P to her nest where Major Monogram communicates to Agent P through a small TV hidden in one of her eggs. Agent E then put worms into her nest, confirming that she is female and that she is expecting the other eggs to hatch soon. She then dropped Agent P off at the docks and isn't seen from again until near the end of the episode, where she swoops down and rescues Agent P and Candace, although she may not have realized this from Heinz Doofenshmirtz's island, which had set to self-destruct.
Like most agents in the series, the first name of Agent E is never mentioned. Since she has a nest, it is possible that she is a female.
Also she once had the duty of hand-cuffing Agent P, along with another agent, due to Perry's doppelgangers being mistaken for Agent P. However, Perry tricked them into hand-cuffing themselves, and ejected himself off the chair and the agents ran after him. ("Cheer Up Candace")