Mr O'Brien used his 70th birthday to fundraise for the Starship Foundation as well, raising $32,000.
Five years later he has decided to do it again with the 75 Years of Frock 'n' Roll show.
"It'll be a nice evening, but most of all it is about turning 75 and still being alive and raising funds for the hospital," Mr O'Brien said.
"It's three quarters of a century, we may as well have a natter about that. Why on earth am I still here for goodness sake?"
Asked about plans for the future Mr O'Brien said: "I don't look too far into the future, I'm not ambitious, I was never ambitious. I like to do things that I enjoy doing, rather than being forced to do them or feeling driven to do them through guilt.
"Sometimes creativity comes out of nowhere. You can sit down and strain your brain and work your butt off trying to come up with something, and truthfully a lot of creativity comes out of nowhere - you weren't sitting there trying to find it, it came out of laziness somehow.
"It's odd how it happens isn't it."
His birthday bash would coincide with Starship's own 25-year celebrations. The hospital is running its own campaign called My Birthday for Starship, where people could celebrate their birthdays by asking friends and family to donate.
Blues band Kokomo would be playing, and one of New Zealand's top piano players Grant Winterburn would also be performing.
For more information on the event, go to: http://premier.ticketek.co.nz/shows/show.aspx?sh=FROCKNRO17&v=TBC or click here