Lou is a Beagle puppy who is the main protagonist in Cats and Dogs, and a secondary protagonist in Cats and Dogs: The Revenge of Kitty Galore.
He is voiced by Tobey Maguire in Cats and Dogs and Neil Patrick Harris in the sequel Cats and Dogs: The Revenge of Kitty Galore. Lou is played by Prada, who also starred as Porthos in Star Trek: Enterprise.
Lou is a Beagle puppy who is born on a farm and lives with his littermates until he is adopted by Mrs. Brody. He is recruited into D.O.G services and is mentored by Butch. Lou eventually becomes the Boss at D.O.G. and fathers several puppies of his own. He currently resides at D.O.G HQ.
Slinky the space dog (Butch), Doom machine (Sam), Baby puppy (The Russian)
In the Films
Lou first appears as a puppy amongst several other beagle puppies at a farm. Eager to become more adventurous, Lou attempts to launch himself through a window with the use of a simple launch system he designed. However, he fails miserably, causing the other puppies to laugh at him as he becomes trapped beneath a bucket from his trap. While Lou is trapped within, the agents sent by Dog HQ arrive and force the beagle puppies to evacuate the area by going down a hole. A few moments later, Mrs. Brody arrives, and is surprised to find the Doberman puppies there instead. However, Lou then makes his way out from underneath the bucket and is quickly adopted by Mrs. Brody, much to the horror of the agents, who were originally sent by Dog HQ to protect the Brody family's research after the kidnapping of the Brody's previous canine companion. Mrs. Brody arrives home with Lou and introduces him to her son, Scotty. Scotty, who is still upset over the loss of his previous dog, initially rejects the new dog, suggesting that they name him Loser. Mrs. Brody, slightly disappointed in her son's unenthusiastic reaction, chooses to name him Lou instead. She then leaves Lou with Scotty and returns to work. Scotty then banishes Lou to the outdoors, and Lou makes a remark on how Scotty appears to be a cat person. Lou wanders down into the yard and spots a bone drifting down from the sky. He curiously inspects it, and, just when he is about to eat it, a dog comes up behind him, warning him not to touch it. He then approaches the biscuit, and, while standing about a foot away, throws a stick at it, causing it to explode. The dog comments on how that was possibly the shortest assignment in history before introuducing himself as Butch. He then begins to question how Dog HQ is training their agents these days as he leads Lou into the dog house. He then opens up the dog house's secret computer system, which Lou finds completely incredible, much to Butch's surprise. Lou attempts to push the "big red button", but Butch prevents him, warning him not to touch it unless told to do so. Butch then explains the mission to Lou before leading him out of the dog house to introuduce him to some friends. Lou is introuduced to Peek and Sam. Butch then comments on how Lou needs to begin his training, and how he probably isn't up-to-date with the latest techniques and strategies. Lou, confused, attempts to impress Butch by chasing his tail. Butch then finally realizes who Lou really is, and storms away to complain about it to Dog HQ. Lou is next seen chasing his tail outside of the dog house with Sam and Peek watching. As Butch emerges, Lou states on how, if he is going to be a secret agent, he should have a code name. As he starts throwing out suggestions, Butch interruptes him with his own sarcastic suggestion before reminding him that he is not an agent, but that he's going to have to help them with the mission anyway. Lou is herded back into the dog house where he is shown the orientation film designed to explain the origin of the theory "a dog is a man's best friend". The documentation is titled "Ancient Egypt". After the film, Lou wonders on how the people could have forgotten what the dogs did for them. After a short explanation is provided to him, Lou is lead out of the dog house. As he, along with Peek and Sam, leaves the yard through a secret panel in the fence, Butch asks Lou if he has any questions, to which the puppy replies by saying he has one. After being prompted to say it, Lou asks what Ancient Egypt was. Butch, slightly annoyed with the puppy's inexperience, simply closes the secret fence panel, leaving Lou without an answer.
Butch served as his mentor to help Lou in his mission to stop Mr. Tinkles.
When Lou meets Ivy she gets his mind off the mission by, “Showing him the finer points of getting his belly scratched."
The night after he gets his assignment he is visited by the Cat Ninjas; Butch guides him to beat the ninjas. Lou gets cocky and the ninjas get away, Butch has a stern word with him.
Afterwards he meets Ivy who tells him that she's a stray and belly scratches him to get his mind off the mission, he really likes it. Over the next little while he comes to be best friends with Scott and comes to help finding a cure to dog allergies.
Just before finding the cure he and Butch stop The Russian Blue cat spy from getting into the lab. Later Ivy appears to Lou and tells him that when Butch is mad he's really sad inside because someone hurt him once. When the cure is found Butch says he has a spot in the academy but doesn't like it when he's told he would be away from his family.
When his family gets kidnapped he tries to stand up for them at dog HQ but fails, the dogs decide to give them up. Lou reluctantly takes the entire dog formula to the cats that ambush him; Butch finds and retrieves him. Together all the dogs find Mr. Tinkles and destroy his plans for world domination.
Lou is injured in the situation but comes to when Scott picks him up and tells him that he's his best friend. In the ending Lou is playing ball with his family, giving up the chance to go to the Dog Spy Academy.