DH has one cute cat suckling his T-shirt right now while he naps on the couch. He'll wake up and grumble about the drool mark but she's too cute to scold for it.
Our oldest cat would suckle (or try to) our earlobes. DSD was a hard sleeper and would wake up with raw earlobes. She also sucked her middle and ring fingers until she was in the 7th grade. One day we noticed she'd stopped doing that. Even in her sleep. My theory is that she couldn't get her fingers to her mouth in the middle of the night with a grey kitty in the way busy sucking her earlobe. I give him all the credit.