Two Agent R's were first recruited by Agent P when he got sent to Africa's Uncharted Gorge by Evil Carl's Go-Home-inator. Later that same summer, one of them got assigned to thwart Heinz Doofenshmirtz when Agent P (in pet mode) was with Ferb at debate camp. Though it eventually managed to defeat the evil scientist, it was almost completely accidental, and led to Doofenshmirtz becoming obsessed with entering contests after being crowned King Pretty Pretty Princess.
Personality and traits
The Agent R's in "Where's Perry (Part Two)" are both excellent at hand-to-hand combat. The Agent R in "What's I Miss?" seems to still be in the early stages of its training, since it did not make any real attempt to defeat Doofenshmirtz and was completely lacking in basic nemesis-to-nemesis manners.