C in English is pronounced "see".
On your telephone, the key with "#" symbol is called the pound sign.
added by edit
Have I stumbled upon a forum with inhabitants completely lacking of a sense of humor?
Well I got your joke and I thought it was hilarious.
This thing: #, has always been the pound-sign to me.
I remember when I first started seeing the hashtag on the internet, oh prolly around the time of #winning, in my mind I always read that as "pound-winning".
Then I heard people saying it out loud as "hashtag winning" and it didn't sound right to me at all.
"see pound" was actually second on my list being "see hashtag", both as ways that I
didn't think it was pronounced.
Next time when you're making a one-liner joke, put a smiley in there so people will know.
Like just type : D (without the space) and it will come out like this:
Otherwise, yes, people will not get the joke and they will respond saying that you are wrong.