Agent D is a dog, its first name is unknown. Not much is known of it but it got first seen in "Traffic Cam Caper". It got injured, along with Agent O, by Dennis the Bunny, the rogue agent, and had its right arm/paw in a sling ("No More Bunny Business"). It was also helping Carl with a drawing of Dennis.
Agent D was first seen in "Traffic Cam Caper". It got injured, along with Agent O, by Dennis the Bunny, the rogue agent, and had its right arm/paw in a sling ("No More Bunny Business"). It was also helping Carl with a drawing of Dennis. Agent D also appeared in "It's About Time!" sitting in the crowd with its nemesis at the Dr. Feelbetter Show. However, it turned out it was a trap. The agent starts fighting once they're freed. It made a small cameo appearance in "Phineas and Ferb Christmas Vacation!" at the O.W.C.A Christmas Party.
It returns in episode "Robot Rodeo" where it got sent out to the L.O.V.E.M.U.F.F.I.N competition and destroy the inators and fight with their nemesis. It appears again in "Rollercoaster: The Musical!" dancing with other agents at the end of the episode. It reappears in Phineas and Ferb The Movie: Across the 2nd Dimension. It went to ambush a group of Normbots with other agents. They were, however, captured and saved by Perry, who was also saved by Phineas and Ferb and used his inventions to defeat the Normbot invasion.
Agent D is a light brown dog with a black nose, dark brown-ish ears, sharp white teeth, a short tail, and an even lighter brown stomach. It is usually seen wearing a dark tan fedora with a reddish-brown band.
In different appearances, Agent D is wearing different fedoras.
In many appearances, Agent D is close to Agent O.
Agent D appears in the online game Robot Riot! as a playable character.
According to its secret file, it specializes in tracking, has instinctive chasing skills, loves group singalongs, occasionally scratches behind ears, and pants in hot weather. (Where's My Perry?)
The image gallery for Agent D (dog) may be viewed here.