Many years ago when I still had my Chinese passport I went to China via Japan and then Hong Kong with the intention of taking the ferry from Hong Kong to ML China. Anyway I did not realize my passport had expired. Not sure how I got on the plane in the first place but apparently no one noticed.
So, I land in Hong Kong and was denied entry due to the expired passport. Options given to me were 1) buy another ticket direct to China or 2) be deported back to Japan. Both options seemed rather ridiculous considering that I am a Chinese citizen returning to Chinese territory (this was in mid 2000s)....
Anyway in the end after like 6 hours at the airport security JAL agreed to vouch for me and I was given a temporary shore pass to get my passport renewed in Hong Kong so I can leave Hong Kong.