Tinkles requiring Charles' research as a ransom for the Brodys, and canines worldwide assemble at a meeting, led by a Mastiff. When the assembly decides not to surrender the formula, Lou confronts Butch. Exposing that he was deserted by his owner, the unsympathetic Butch leaves Lou behind. Desperate, Lou brings Mr.
Butch, understanding what has occurred, stages a raid of Mr. Tinkles' factory where mice are being prepared to spread the mass-produced allergy. While Butch, Ivy, Peek, and Sam battle Tinkles' cat forces, Lou releases the Brodys and Calico, who was betrayed by Tinkles, revealing to the household that he can speak.
Butch rescues the apparently dead Lou, tearfully confessing that Lou was right to enjoy his adoptive family, and Lou awakens. He chooses to go back to a normal family pet's life with the Brodys until he can function as a mature agent. Meanwhile, Tinkles is sent to cope with Sophie and her three sisters, with even more humiliating clothing as penalty for his actions against the pets.
Alec Baldwin as Butch: An Anatolian Shepherd, a skilled field agent, and Lou's mentor. Sean Hayes as Mr. Tinkles: A Persian cat; the leader of the cat agents, who looks for to beat all pet dogs and rule the world. Did you see this? as Ivy: A Saluki; "domestically challenged" former-dog representative who has a history with Butch.
Charlton Heston as The Mastiff: An English Mastiff, and the leader of the pet agents. Jon Lovitz as Calico: An Unique Shorthair cat, and Mr. Tinkles' second-in-command. Joe Pantoliano as Peek, a Chinese Crested Pet representative. Michael Clarke Duncan as Sam, an Old English Sheepdog agent. Billy West as Ninja Cat # 1 Danny Mann as Ninja Cat # 2 Glenn Ficarra as Dimitri Kennelkoff/ The Russian: A Russian Blue feline agent, who is sent to detonate an explosive at Professor Brody's lab.
Lou's dog house was filmed on Stage 1, Mr. Mason's workplace and the interior of the tree gathering factory was filmed on Stage 2, and the worldwide conference with the canines was filmed on Stage 3, while the backyard of the Brody house was recorded on the studio backlot, and the front outside of the Brody house was shot at 1661 W 45th Avenue in Vancouver.
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