Agent O is an owl brown-ish orange in color. His first name is unknown, not much is shown of him but he was seen in the Traffic Cam Caper episode. He was injured, along with Agent D by Dennis and had his left foot in a cast ("No More Bunny Business").
Agent O probably broke his left foot the same way Agent P fell in the sandpaper factory because of Dr. Doofenshirtz. (Hail Doofania!)