Doncaster went down 21-13 to Thanet Wanderers at the home of England Rugby in 1997 following a memorable cup run in the national knockout competition.
A controversial knock-on infamously helped the Kent side to victory in front of a 5,000-strong crowd.
Players and fans were reunited at Knights’ recent game at home to Ampthill at Castle Park.
Organiser David Senior said: “Everyone played their part in the 1997 season.
“It wasn’t just the 15 players on the pitch – it was everyone who manifested the success. That’s why we’ve made this event so inclusive.”
Ex-player coach Kevin Westgarth said: “I don’t miss an opportunity to come back here, it’s great, I love it.
“Every time I come back here it’s just wonderful.”