The Mouse Agent is a small-sized agent has been seen in some episodes. In his/her first appearance, he/she's seen riding the elevator alongside the unnamed bear agent, unnamed crocodile agent, and others (" Isabella and the Temple of Sap ").His/her appeared again in " Phineas and Ferb Christmas Vacation! " dancing with the other agents. His/her next appearance wouldn't be until Phineas and Ferb The Movie: Across the 2nd Dimension , where he/she's seen attacking Normbots alongside his/her fellow agents. He/She appeared again in " Agent Doof " and "
Phineas and Ferb Save Summer "
His/her appearance is that of an ordinary mouse with a fedora.
His/her boss in the
Agent M can team with the other Agents well, as it appears, in the 2nd Dimension movie. He/she is on good terms with Perry, and others, even his/her actual predators, so it can be assumed it does have friends in the Agency.