Are there other biblical references where angels are disguised as humans? I was reading Genesis 19: Sodom and Gomorrah Destroyed and in the first verse, two angels are greeted by Lot as they arrive at the gates of Sodom. But instead of the "do not be afraid" speech that angels typically say, Lot offers to wash their feet and insists they spend the night at his house. What is going on here? I can't find a verse that specifically states the angels were disguised as men, but in verse 5, the people of Sodom say, "Where are the men who came to you tonight? Bring them out to us so that we can have sex with them."

This would be really weird if the angels weren't disguised (actually it's weird either way) so I'm going to go ahead and say that they were disguised as men. Are there other biblical references where angels are disguised as humans?
Apparently, some in New Testament times were familiar with some such incidents, and did not find it unlikely that it would happen, as related in the book of Hebrews:


  Hebrews 13:2
  
  Be not forgetful to entertain strangers: for thereby some have entertained angels unawares.