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16 February 2019, 11:38 | Updated: 16 February 2019, 11:40
County are 82 places below Premier League leaders City in the football pyramid, but Flynn believes his Sky Bet League Two underdogs can add Pep Guardiola's side to the list of recent Rodney Parade victims that includes Leeds, Leicester and Middlesbrough.
"If we win this, whether it's extra time or penalties and I don't care how we do it, it will be the biggest shock in FA Cup history," Flynn said at his pre-match press conference.
"I say that with the biggest respect to other big giant-killings.
"My reasons for that are because of the sheer gulf in finances, the quality of the players Man City have, the level they are playing at, and that they have the best manager in the world right now.
"So for those reasons it will be the biggest shock the FA Cup has ever seen."
Newport have won only twice in the league since the end of November, a run which has seen the Exiles slump out of the League Two play-off positions and in to 15th place.
Yet in that time Newport have beaten Wrexham, Leicester and Middlesbrough in the FA Cup to reach the fifth round for the first time in 70 years.
"Of course there is," Flynn replied when asked if a shock to end City's hopes of winning an unprecedented quadruple was possible.
"Otherwise I'd just turn up, give them the game, say 'let's shake hands' and walk off.
"Who said we were going to draw with Tottenham last season or beat Leicester, Leeds and Middlesbrough? These players have a knack of rising to the occasion.
"We won't just be sitting back, no chance. I would rather get thumped doing it properly than losing 1-0 with no ambition.
"I want to give the supporters something to cheer about and these players have to believe, which I know they do, that they can cause an upset."
Flynn says it will be an "honour" to share the same touchline as City boss Guardiola.
The 38-year-old studied for his coaching badges alongside City assistant coach Mikel Arteta when Guardiola's tactics and philosophy was examined on the Football Association of Wales course.
"As part of it, we all had to study a different world-class manager," Flynn said.
"I actually had Diego Simeone, one of the others had Pep. I have asked for it (coursework) but to no avail.
"Pep's bordering on a genius the way he goes to different countries and changes their way of thinking. He makes them believe in his philosophy, and that's not easy.
"Everyone says he just goes to the big teams, but he went to Bayern Munich when they won absolutely everything and he changed the whole philosophy to be in sync with what he believed in.
"Seasoned world-class players like Philipp Lahm bought into that and produced some of the best football Bayern have played.
"He might be at the top level, but I've got no doubt that he could do it in League Two and any aspiring coach or manager needs to pay attention to that without losing their own identity."