Wrexham, the Welsh side which competes in the fifth tier of the English league system, was moments away from toppling a Sheffield United side which is closing in on promotion to the Premier League.
Paul Mullin's 27th goal of the season had put Wrexham 3-2 ahead in the 86th minute, with its visitor to the Racecourse Ground by then down to 10 men after Daniel Jebbison was sent off.
Movie star Reynolds, co-owner of the club who have been the subject of a major documentary series during his two years at the helm, was getting ready to celebrate a huge moment in Wrexham's history.
But Sheffield United had not read the script and rode roughshod over the fairy tale ending when John Egan scored in stoppage time to earn a draw, meaning the teams will go to a replay at Bramall Lane.
Rob McElhenney, the actor, writer and producer who also bought into Wrexham, was not there to witness the high drama first hand, but Deadpool main man Reynolds could be seen holding his phone out to the raucous atmosphere with the It's Always Sunny In Philadelphia star on the other end of the line.
It was a game that was shown live on the BBC, with National League leaders Wrexham showing why they could well be back in the Football League next season.
Reynolds wrote on Twitter: "When @RMcElhenney and I got into this it all felt so impossible. But impossible is @Wrexham_AFC's favourite colour.
"That was one of the most exciting things I've EVER seen. Thank you each and every Wrexham supporter who came out and aimed your heart at that pitch tonight."
Reynolds posted a picture of himself with Premier League record scorer Alan Shearer and Manchester United and Wales legend Mark Hughes, who were working as pundits at the game.
Shearer replied to Reynolds' post, writing: "Thank you for your hospitality today!!! What an incredible atmosphere and game. A living breathing screaming nightmare!!!!"