I used to have a cat who would get obsessed over my shoes and my mom's after we'd gone outside, come back in, and taken them off. He was indoor cat, so the only time he got to go outside was when we supervised him, and he would go and rub his face all over our shoes, rolling on them like they were catnip and drooling all over them. He drooled whenever we got him purring too hard, too. He was a super friendly cat and loved sitting on our laps while we watched movies on the couch, especially if we draped a blanket over our legs, so "purring too hard" happened often.