Iirc there's around 20 clubs that get involved - mostly catering to incoming international students. Not many locals enrol into sem 2 - sem 2 enrolments mainly consist of internationals because school for them generally ends on May/June and uni for them starts at around August/September or so.
Not as big as O-Week in Semester 1, I went there last year and all the club stalls and activities were outside the CLB courtyard. There are freebies and food here and there, but not much.