: It is Annie's 16th birthday. Naomi, after seeing Annie and Ethan kiss, invites Annie's ex-boyfriend Jason from Kansas as a "gift" to stir up trouble.
: During the party, Harry's 22-year-old illegitimate son, Sean, arrives for the first time. [S1E10] Games People Play
While "" is the title of the entire series, the 10th episode of Season 1 is titled " It Happened One Night ". "90210" Games People Play (TV Episode 2008) - IMDb : It is Annie's 16th birthday
: Kelly returns from her trip and reveals what happened with Dylan. She also confronts Ryan about rumors regarding a student hookup. after seeing Annie and Ethan kiss