When I was a kid, my dad started getting these mysterious dirty greeting cards delivered in the mail. Because they were unsigned and there was no return address, there was no way to tell who was sending them or why. We could tell it was a male's handwriting on the envelope, but that was about it. I don't remember how, but my dad figured out it was a good friend of his who would pick up a dirty greeting card in whatever town he was traveling to for work and send us these hilarious cards.
Even after we knew it was him, he continued to send them every now and again, still with no signature, and I would be the first to rip open the envelope to see the dirty jokes and naked people, even if they were usually cartoons - they were still naked.
It was really sad to hear that this friend died a few years back. I wish I could have known him more as an adult because he seemed like my brand of people.