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Ahead of Monday's fifth-round tie at the Greenhous Meadow, the League One side's boss Micky Mellon has already gathered a battle plan that cannot fail to strike a chord with the competition's romantics.
No-one loves roughing up the elite more than Sam Allardyce (just ask Arsene Wenger) so it is fortunate that Mellon is big pals with Big Sam.
Friends from having played under Allardyce at Blackpool, Mellon has the perfect inside track on how to upset the odds.
The current Sunderland boss is the last man to beat United domestically, thanks to their 2-1 win last Saturday in the Premier League, and Mellon admits he will use all his old manager's know-how.
"I'm seeing Big Sam and see what his plan was and if there's any help we can get from that then we will," he told BBC Radio Shropshire.
"I'm a big schoolboy when it comes to football and to be able to prepare my team to face Manchester United is a fantastic moment in my career."
Perhaps the magic and miracle of cinema can also provide a source of hope.
If Shrewsbury had Pele up front, Ossie Ardiles in midfield and Bobby Moore at the heart of the defence, they could well afford Michael Caine at left-back and still beat Manchester United, or anyone else for that matter.
But, unlike the Germans in the iconic 1981 film Escape to Victory, they did defeat a side that contained more than a hint of that heroic Allied XI.
Russell Osman, John Wark, Kevin O'Callaghan and Paul Cooper (body double for goalkeeper Sylvester Stallone in the film) were all in Bobby Robson's stylish Uefa Cup-winning Ipswich side that lost 2-1 to Shrewsbury in the fifth round in February 1982.
But if it is all going pear-shaped at half-time on Monday for Town, in keeping with the film, they can always dig an escape tunnel under the bath.
In addition to the Tractor Boys of '82, Shrewsbury saw off another top-flight side Manchester City on their way to the sixth round in 1979 - still their best run in the competition to date.
More recently, it was Kevin Ratcliffe's side that wrote the third-round headlines as two goals from Nigel Jemson, including a last-minute winner, dumped Ratcliffe's old club and five-time winners Everton out in 2003. It gave a 17-year-old Wayne Rooney an early introduction to the FA Cup's capricious nature.
If you only looked at the visitors' FA Cup record, you would tell the Shrewsbury squad to stay in, watch their favourite box-sets on Monday, and give the tie a wide berth.
Only Arsenal can boast a better record than United's 11 Cup wins, but Town fans will point to the fact that they have not won the famous old trophy since beating Millwall in Cardiff in 2004.
And like a lot of the big boys, they have not been immune to the odd upset over the years.
Bournemouth's famous win over holders United in the third round in 1984 still ranks as one of the competition's biggest-ever shocks and League One Leeds United's victory at Old Trafford six years ago is another Red Devils fans want to forget.
Exeter City and Burton Albion - both Conference sides at the time - also forced third-round replays in 2005 and 2006 respectively.
So that, together with the scale of United's current injury crisis - 14 players struggling at the last count - is surely grounds for optimism?
Aberdeen-born Jack Grimmer will always love Manchester United. Sir Alex Ferguson's masterminding of the Dons' stunning Cup Winners' Cup triumph over Real Madrid in 1983 saw to that.
"It's something that'll never ever be forgotten - he's a folk hero at Aberdeen and what he went on to do at United will never be matched," Grimmer, who is on loan at Town from Fulham, said.
The Scot has taken some of that Ferguson gold dust and sprinkled it over his two loan spells at Shrewsbury in the last two seasons.
A League Cup cracker with Chelsea last term preceded a stunning last-gasp winning goal in that crazy finish against Sheffield Wednesday to set up the shot at United.
Grimmer has been nursing a tight hamstring but says nothing is going to stop him being part of another huge occasion.
"If I broke my leg, I'd still be going out there - it's a game everyone wants to play in and you only get a handful of these matches in your career," the 22-year-old said.
And maybe another winner?
"That's what I'm looking for. That's what dreams are made of so if anything remotely close to that happens it'll definitely top Sheffield Wednesday.
"It'll be a special night with a packed ground and if the crowd can get behind us an upset could definitely be on the cards."
Another one with a taste for the big occasion is Andy Mangan.
The 29-year-old striker, on loan from Tranmere, shone in last season's League Cup run, grabbing the only goal as Premier League Leicester City were knocked out in the second round.
He then got the Shrews' equaliser in their pulsating fourth-round tie with Chelsea, before the Londoners squeezed through 2-1.
Like all the best stories, he suffered disappointment, leaving the club last summer before returning in a blaze of glory, netting the winner on his first appearance back at the club against Cardiff City in the third round last month.
"Manchester United are a superpower," Mangan said.
"Everyone knows them and to be involved in that is really magical - when they got pulled out of the hat I was jumping around the room.
"I'm in awe of some of their players but I'll try and perform, and to play against them makes me very proud."
James Bond, BBC Radio Shropshire sports editor
"TV cameras at training, the national media descending on the club... normally pre-match interviews involve Micky Mellon and his players chatting to BBC Radio Shropshire and the Shropshire Star.
"But attention is very much focused on the lowest-ranked club left in the FA Cup and Shrewsbury folk have been talking about little else.
"The ticket office has been besieged. Local musicians have written songs about the big game. Even special bread has been baked! It's been an unforgettable experience.
"Town fans fancy some giant-killing. A 2-1 win is a popular thought."
Interviews with BBC Radio Shropshire's James Bond.
Shrewsbury Town will not be short of inspiration when they try to knock Manchester United out of the FA Cup.