Lou is a beagle puppy who is currently head of D.O.G. even though he refused to be an agent at the end of the first movie.
Slinky the space dog (Butch), Doom machine (Sam), Baby puppy (The Russian), Father of the year (nobody)
In the Films
Lou first appears asa beagle puppy along with other beagle puppies in a farm. While alll the other puppies seek a comfortable home, Lou seeked adventure. Lou tries to jump out the window but fails, and the other puppies laugh. Soon, D.O.G. sends in agents to get a home after recieving the news the Brody family was adopting a puppy there.
When Lou was picked due to a mistake, Butch was sent to train him and partner with him.
In the end, at a christmas tree factory, he defeated Tinkles and chose his family over being an agent. Suprisingly, he appears as leader of D.O.G. in Cats and Dogs: The Revenge of Kitty Galore.
In Cats and Dogs: The Revenge of Kitty Galore, Lou is head of D.O.G. and wears an office uniform for dogs.
Lou is mated and has puppies.