In retrospect, here are a compilation of various cast interviews (mostly, you've read/heard them from the P&P DVD extras) and what the cast said their experiences were like filming P&P movie and bonding with each other...
"Filming Pride & Prejudice (2005) was a joy and made for one of my happiest summers ever. "It could well be that the story brings out the best in people - and it sounds so cheesy, but we really did behave like a family. The girls playing the younger sisters had never been on a film set before and wanted to socialize all the time, so we picnicked, hung out in a beautiful country house and went swimming naked in a lake. It was idyllic." - Rosamund Pike
About her Pride & Prejudice (2005) co-stars: We were like one big family. We took over the house. It was so much fun. Brenda Blethyn (Mrs Bennet) mummied us all - when we had days off she took us on day trips to a llama farm. - Carey Mulligan
What do you remember about that filming experience?
Jena Malone did, because she played almost a twin, so I basically did everything she did. And that was how I got through it ... It was an incredibly tight gang of people. Joe Wright does that brilliantly, he builds families while he builds his casts and he makes you spend a lot of time together, so you do kind of form those relationships. And that comes off in his films really well. - Carey Mulligan (via movie fone)
“I was a real tomboy until was 15 – I didn't have my first kiss until a month away from being 16. So I just copied everything Keira did for weeks. She is still amazing to me.”
“That was a mad hippie summer – a party every weekend, lots of jumping naked into the lake. And I ate everything; my face ballooned. I realized catering is a very dangerous thing!”- Carey Mulligan
Tom Hollander: It was just me and Keira and Talulah... and all the girls playing Sardines in a cupboard. That was one of the happiest days of my life. [laughs...and dances in the background as Mr. Collins, lol]
Talulah Riley: To bond and to get to know the house... we decided to play the game Sardines... where one person hides and then everybody goes to look for them.
Brenda Blethyn: It's been so happy, a kind of idyllic in that house. And the friendships and the camaraderie, it's just heaven. And I don't want it to end, to be honest.