When the woman says "GET IN!" it is a cry of joy. She does this because she must be from Belfast, too. She is cheering for her home's representation. It's very Northern, and might be used in response to good news. Your child got top scores in an exam ? GET IN! Your favourite sports team won ? GET IN! When David Walliams says "Get into who, darling ?" he's being sarcastically comedic, or "sassy". He pretends not to know what it means, because it wouldn't be very upper class to know Northern slang. You see, "getting in" to someone implies s*xual penetration. Obviously she doesn't mean anything s*xual by her cry of joy. I hope this helps!

I just found this video: https://www.youtube.com/watch?v=cGb7fbBXw_A It is at the 30-second mark. Where are you from, David and Darren? We're from Belfast. (Get in!) Get into who, darling? I am Canadian, and I have never heard the expression "get in" like this. I wish I could help, but this sounds more like something that someone from Britain can explain. When the answer is "get in to who" he is just responding to her. The real question is what is the "get in" expression?

When the woman says "GET IN!" it is a cry of joy. She does this because she must be from Belfast, too. She is cheering for her home's representation. It's very Northern, and might be used in response to good news. Your child got top scores in an exam ? GET IN! Your favourite sports team won ? GET IN! When David Walliams says "Get into who, darling ?" he's being sarcastically comedic, or "sassy". He pretends not to know what it means, because it wouldn't be very upper class to know Northern slang. You see, "getting in" to someone implies s*xual penetration. Obviously she doesn't mean anything s*xual by her cry of joy. I hope this helps! EDIT: Accidentally commented instead of submitting it as an answer. :)

It must be British slang. I am from the US and have never heard that

Hi Michael, to be honest I still don't understand what 'Get in' and 'Get into who' mean.