Sortof an inside joke thing -- a g-man is a government man, usually from the FBI and German Shepherds are a popular breed for K9 units. Lame, I know.
Breed: German Shepherd
Gender: The lineart's male, so that's what I'd envisioned, but he doesn't have to be a he.
Personality: Exceedingly aggressive when feeling threatened; has a somewhat irrational fear of being picked up even though he weighs roughly 80lbs (he's quite large); well-behaved with children and adults and most other animals, except porcupines