Sergei the Snail

 also known as Agent S, is a snail agent working for the O.W.C.A.. It was briefly assigned to Heinz Doofenshmirtz when Doofenshmirtz was downgraded as a low threat villain ("Oh, There You Are, Perry").

Background Information

 * Due to the slow speed at which snails travel, Agent S is likely only assigned to low-threat villains. Also, even if Agent S proves himself useful at stopping villains, he would still have to move at a slow speed from his spot of entrance to the scene of action, thus it would be risky to fight more powerful villains.
 * His gender is both male and female as most Gastropoda, which includes snails, are both male and female.
 * His name is revealed in "Perry the Actorpus", when he fights with Heinz Doofenshmirtz.
 * He's the third minor agent to be named. First were Herman the Hedgehog and Peter the Panda. It is the first to be named after its first appearance.

Appearances

 * "Oh, There You Are, Perry"
 * "Perry the Actorpus"