Two Agent R's were first recruited by Agent P when he was sent to Africa's Uncharted Gorge by Evil Carl's Go-Home-inator. Later that same summer, one of them was assigned to thwart Heinz Doofenshmirtz when Agent P (in pet mode) was with Ferb at debate camp. Though he 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)" were shown to be excellent at hand to hand combat.
The Agent R in "What's I Miss?" seems to still be in the early stages of his training, since he did not make any actual attempt to defeat Doofenshmirtz and also was completely lacking in basic nemesis-to-nemesis manners.