Happy friends (published under CC0 Public Domain, source: https://pixabay.com/en/children-silhouette-cheers-positive-479692/)
Meaning: Enjoy the company of others very much.
Polish analogue: Przypaść sobie do serca.
An example of use: Peter invited lots of different people to his 40th birthday and I was slightly concerned we might not like each other, but in the end we all got on like a house on fire and had a really good time.