Zack Shada and Jeremy Shada, who play young versions of brothers, Liam and Charlie, are actually brothers in real life.
The woman whom Charlie saves from a mugger is Nadia, the woman Sayid tortured (and freed) in Iraq, and whose house was inspected by Locke.
Charlie's flashback of him saving a woman from a robbery occurs on the same day as Desmond's time flash in Flashes Before Your Eyes (2007), as indicated by the circumstances: Charlie playing and singing "Wonderwall" on the street, when it suddenly starts to rain. The main difference is that Desmond does not interfere in Charlie's recollection (since Desmond's flashback was probably an elaborate 'vision', and not an actual experience).
When Desmond and Charlie are preparing to go to the station, in the background there's the unfinished church that Mr. Eko built.
Charlie mentions to Naomi that his band Driveshaft got it's start at the night & day bar on Oldham Street in Manchester, this is a real life bar in Manchester