Here is something that I found on Instagram the other day:
"The funny thing about introverts is once they feel comfortable with you, they can be the funniest, most enjoyable people to be around. It's like a secret they feel comfortable sharing with you. Except the secret is their personality."
I can count many times that I have heard people say:
"You are quite funny."
"He is hilarious."
"He's a bit of a hard case." (New Zealand slang for funny person.)
"You are quite amusing when you come out of your shell."
I'm sure many people who identify themselves as an introvert have heard this before. It is entirely true. When we start feeling comfortable around certain people our true personality will come out. Sometimes it will take five minutes, some other times it might take years to feel truly comfortable.
If someone who is usually quiet around you suddenly seems to come out of his or her shell, take it as a huge compliment. They like you. They want to share things with you and encourage them to talk more.
Whatever you do, don't try to shut them up because you don't feel comfortable that they are talking more. You will just force them to go deeper and deeper into their shell than they were in before and then it will be back to the proverbial blood out of a stone and that situation is not good for anyone.