They were hugely popular and spawned tons of merchandise. Sleeping bags, a toothbrush set ( which I had ), Lunchboxes ( which I also had ), Shrinky Dinks, Colorforms ( had those too ), Cookie jars, posable figures and a whole host of other products.
There was also an animated series which debuted in prime time with an hourlong special. The special is a tad different from the series that followed it. Characters that appeared in the special ( Barkerville, Scrounger, ) were absent in the series. Other characters included Cooler ( the leader ), Whopper, Bright Eyes, Nose Marie and Howler. They lived at the dog pound and helped homeless dogs find homes while outwitting the villain of the series, Katrina Stoneheart.
Of course I had my own Pound Puppy, a sad faced grey bulldog named Elliott. Like the Koosas mentioned elsewhere on this site, you could send in forms in order to "adopt" your Pound Puppy.What you got in return I'm not sure as Elliott's stuff never came in.