A few more references I made with previous references (although no.1 could probably count as part of the girls arrival from the official easter egg list):
1) When the girls were talking about Ongar on the roof, Roxy said "It's hardly Ibiza is it", echoing her very first impressions of Albert Square when first arriving in 2007.
2) Ronnie said she would like them both to open a bar in Ongar, and of course they opened R&R together not long after first arriving.
3) Ronnie ended up trying to save Roxy in another "watery situation", likewise New Year's Day 2009 when Roxy fell through the ice on that lake with Sean Slater. Roxy was in trouble then and Ronnie dived in to save her, just like tonight. Even her scream of "Roxy!" just before she dived into the pool.