Watch: Back To The Future stars Michael J. Fox and Christopher Lloyd hug at ComicCon
The pair - who starred as teenager Marty McFly and his eccentric scientist neighbour Emmett 'Doc' Brown in the 1985 cult hit time travelling adventure - both attended the Back to the Future Reunion at New York Comic Con on 8 October.
Fox, 61, said: "The best part of this movie was working with Chris."
Lloyd, 83, added: “There was immediate chemistry, as they say."
As the pair greeted one another on stage they put their arms around each others shoulders, before Fox put both arms around Lloyd and leaned his head against his chest, to rapturous applause from the crowd.
Lloyd then helped Fox to sit back down on the sofa.
Fox was diagnosed with Parkinson's disease – a neurological condition that affects body movement – in 1991, when he was just 29.
Speaking about living with his condition Fox – who needed support to walk on stage due to his tremors – said: "Parkinson's has brought people who are still coming in, but it's a gift, and I wouldn't trade it for anything.
"People like Chris have meant so much to me, and so many of you have too.
"It's not about what I have, it's about what you've given me: a voice to do that and help people."
The pair starred together in two further Back To The Future movies in 1989 and 1990.
Fans of the trilogy shared their delight and emotion on social media after seeing the touching reunion.
One tweeted: "If you were a teenager in 1985, then Michael J. Fox was your guy. Marty McFly in Back to the Future is the coolest teenager in cinema history. Watching him hug Christopher Lloyd like this is so beautiful."
Another teased:" Michael J. Fox and Christopher Lloyd reunited at NYC Comic Con today *I’m not crying, you’re crying."
One fan said: "Michael J Fox and Christopher Lloyd. This iconic duo from Back to the Future, always in my heart."
The scene was described as "Such a beautiful moment" and "the best" by movie-lovers.