The courier who frequently delivers you letters to start quest chains got killed outside of Riften by the guards. Not wanting to let a perfectly good dead body go to waste I decided to loot it, including his clothing. Apparently the courier re-spawned and now is not wearing any clothing when he delivers.
It is a little awkward when I am walking through a city and a naked man walks up to you and says
I have special package for you, your eyes only!
Is there any console command to re-spawn him to make him come back with his normal clothing?
UPDATE: Proof that it happened.
Also another note, reverse pickpocketing clothing did not fix it. In fact he had clothing in his inventory already that he chose not to equip.
The v1.9 patch has fixed this:
Fixed rare instance of couriers who would appear only dressed in a hat.
As for why it took Bethesda more than a year to fix this, I have no idea.
Before the v1.9 official patch was released, the Unofficial Skyrim Patch had a fix for that:
The courier who delivers various letters should no longer show up naked occasionally.