Sadie cleans Riley's ears and eyes, and sometimes other parts of his face. She also cleans her own paws almost obsessively - she'll make a huge wet spot on the sheets if she does it in bed, and you don't stop her. She will also lick her paws and use them to clean her face, like a cat.
The vet told me that if she is cleaning one of Riley's ears more than the other, check it for an infection (it'll smell funny if it has an infection, and that's what's drawing her to it). I noticed this once, and sure enough, he did have an infection in that ear.