I was watching season 1 episode 7 “the monogamists” and see two actors that appear later in the series.
Later he appears in Season 2 Episode 15 “Shortcomings” as Vaughn, the short story writer (premature ejaculator):
The second one plays Big’s friend at a party:
And then in Season 4 Episode 2 “The Real Me” he plays Carrie’s photographer when she is a model in NY Style:
I checked my Sex and the City Kiss and Tell book and on page 55 found this behind-the scenes tidbit that confirms the first guy –