Thanks to Anthony for the following from IMDB.
Episode 5.02 - The Lie
Todd Bryant who originally it just said was going to appear in episode 2 "the lie" but it didn't say the role. well now on IMDB it says he is cast as "Mattingly"
Episode 5.04 - The Little Prince
IMDB says Young Danielle Rousseau played by Melissa Farman AND normal Danielle will appear in episode 4.
Source: IMDB