Slinky the space dog (Butch), Doom machine (Sam), Baby puppy (The Russian)
Lou first appears as a 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 Lou's siblings 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. Surprisingly, he appears as leader of D.O.G. in the second film.
- Lou is mated and has puppies.
- We can assume he lives with his mate. We can assume this because he says in the second film "my wife is at the groomers."
- The statement above may also show he still lives with the Brody family, as who would take his mate to the groomers.