Maybe it's not a hairball. Maybe Kewpie ate too much food or drank too much water, or too much grass or not enough grass, or ate a leaf or got into something in the trash or re-ate her puke or ate her poop. Basically, if your dog is hacking something up, just assumed it ate the wrong thing.
As noted in the first strip--and in every other strip he wears that red sweater in, Brutus does wear only V-neck sweaters. But considering both the Thornapples and the Gargle seem to have big noses in the family, you would think Mother Gargle would've thought of that.