I know we've had these threads before but I love them 
So my creepiest reaction has been a woman coming out of the loo as I was waiting to go in - she made a beeline for me straight away, massaged my abdomen firmly anf hissed "Now I wonder what's in there" into my ear. 
The most socially awkward one was my 82yo NDN when we told her we were having twins. She is a very naice older lady, very active in the local community, always perfectly made up, etc. She looked DH up and down and said conversationally, "What a magnificent stallion he must be!"
There is just really nothing you can say to that.....
Care to share yours?