Here is a look back at a selection of players who have turned out for both sides down the years. How many of them do you remember?
13. JORDAN BOWERY
Current Stags star, utility man Jordan Bowery, played for Orient in the 2016/17 season. Photo: Pete Norton
14. OTIS KHAN
Midfielder Otis Khan joined Stags in 2018 for two seasons. He signed an 18 month deal with Orient last week. Photo: Lewis Storey
15. STEPHEN DAWSON
Popular Irish midfielder Stephen Dawson delighted fans with his tough tackling. He played over 125 times for Stags from 2005 but, on relegation to the Conference in 2008, elected to leave and joined Bury followed by two years with Leyton Orient. Photo: Tony Stocks
16. SHAQ COULTHIRST
Striker Shaq Coulthirst came through the ranks at Tottenham from where he went out on loan to Leyton Orient in 2014. He joined Mansfield on loan from Peterborough in 2015 and netted five times in 20 league games, but he was then allowed to join Barnet on a permanent and spent three seasons with them. Photo: Pete Norton