In general, voice actresses are typically cast as male pups (notably Cree Summer, Kath Soucie, Grey DeLisle, and EG Daily). This makes the irony of Patches' two male friends who berate him for being "girly" all the better.
Talking to Himself: The Pound Puppies' voice actors also provide the voices of their Kennel Kitten counterparts. Additionally, Alanna Ubach and John DiMaggio frequently voice pups, dogs, cats, and humans they cross paths with.
Eric McCormack voices both Lucky and Ace, which is appropriate, since the latter is basically a cat version of the former.