Reynolds and McElhenney are co-owners of League One leaders Wrexham, while Brady is a minority shareholder in promotion-chasing Birmingham.
Both teams have made unbeaten starts to the season and their celebrity powerbrokers are fired up for the crucial clash at St Andrew's.
McElhenney took to X, formerly known as Twitter, to share a message with Brady ahead of the fixture, writing: "See you next Monday, Tom Brady. Should be an absolute banger."
Deadpool star Reynolds and It's Always Sunny in Philadelphia actor McElhenney joined forces to buy Wrexham in 2020.
The surprise takeover was chronicled in the 'Welcome to Wrexham' documentary that gave the previously unheralded Welsh club a cult following around the world.
Wrexham have enjoyed a remarkable period since they were sprinkled with Tinseltown stardust, rising from the fifth-tier National League to League One with back-to-back promotions.
In stark contrast to Wrexham's rise, Birmingham have endured the darkest period in their recent history since Brady came on board as part of a takeover by US-based Tom Wagner's Knighthead group in August 2023.
Brady and Wagner have been friends since their children attended the same New York school, investing in various projects together including a Major League Pickleball franchise.
Brady, who retired in 2023 after 23 seasons in the NFL, was a seven-time Super Bowl champion as quarterback for the New England Patriots and the Tampa Bay Buccaneers.
'Glitz and glamour'
The 47-year-old fitness fanatic's Birmingham involvement includes "working alongside the sports science department to advise on health, nutrition, wellness, and recovery systems and programmes".
Brady travelled to Birmingham last season to watch a game, buying drinks for fans in a local pub,
But his investment hasn't gone to plan so far, with the Blues relegated to the third tier last season for the first time since 1995.
Manchester United legend Wayne Rooney, who presided over a miserable 83-day reign that ended with his dismissal, was among six managers used by Birmingham in a chaotic campaign.
Former Tottenham assistant coach Chris Davies has been tasked with restoring order at a club that last played in the Premier League in 2010/11.
Davies has been backed with an outlandish budget for League One that included smashing the division's transfer record to sign Jay Stansfield from Fulham for a reported fee in excess of £15 million.
Birmingham have made a strong start with 10 points from a possible 12, while Wrexham have won four and drawn one of their opening five fixtures.
"It's the Hollywood derby! There's so much glitz and glamour about it," Sky Sports Football League pundit Don Goodman said.
"It brings eyes from around the world to the lower levels of the EFL."
Adding spice to the fixture, it was reported in the close season that Birmingham's owners were keen on staging the Wrexham game in the United States.
Wrexham weren't interested in the mooted plan, which had little chance of earning Football League support, and Reynolds was quick to shoot it down.
Replying to a tweet criticising Birmingham's reported idea, he said: "I agree. And that's why there have been no talks."
The battle for League One supremacy between the stateside stars is only just beginning, with plot twists aplenty in store.
