When it comes to the world's most famous haircuts, 'The Rachel' is definitely up there. But we know that Aniston isn't a big fan of the style, famously saying: 'I think it was the ugliest haircut I've ever seen. What I want to know is, how did that thing have legs?'
And now we hear that McMillan, Aniston's long-time hairdresser, was stoned when he gave her the chop back in 1994.
'Im 14 years sober, so I feel safe enough to say that,' he says in a new interview.
Aniston has since become known as much for her hair as her romantic life and acting roles, so it made sense for the actress to buy into Living Proof haircare brand - a new venture that she announced in October, and on which she and McMillan are again collaborating.
'I want to expand my world to businesses other than entertainment,' she said. 'Im trying to figure out how to enter into that entrepreneurial area of my life.'
So why Living Proof? It was her secret penchant for watching the Science Channel that spurred on her to decision to get involved with a hair company comprised of a group of MIT scientists. 'I get sort of mesmerised by [the Science Channel] I get stuck on it,' she said. 'Its like watching an infomercial.
'I always did like science class when I was in school. How things work interests me.'
When the Living Proof team took to the streets to find out what people thought of their own hair, Aniston realised the negative way she felt about her own hair was a common trait in others.
'I was looking at these girls who were not loving their hair, and Im thinking, "You have beautiful hair!" Its always funny, our perspective of ourselves and how incorrect it usually is. We always seem to want something we dont have. And its a shame, because theres so much beauty to be appreciated in the world. We spend so much time not loving what weve been given and trying to make it look different.'
It's still early days for Living Proof and Aniston's partnership - she announced her involvement back in October - but she did reveal that the scientists are already working on a few of her dream products.
'Were just getting into the creative stuff. I have a couple of ideas, but I wont blow it now,' she said. Watch this space.