I don't know how well known the crossover characters are outside of the UK. I would be very surprised to find a UKian with children (especially girls) under 5 who didn't instantly recognise them.
Summary: Sam and Dean meet a little boy; he has a little sister who is small and very funny....
Dean is my Favourite and my Best by chaletian
(If I was on a team, this would be posted for Team Dean)