The National League North side earned a 2-1 win over Championship promotion contenders Ipswich at Portman Road to earn their spot in the fifth round.
Picking up the call, Fagan exclaimed: "I'm here and the lads are too," with a packed Maidstone team bus cheering and lifting their drinks.
As well as topics such as a new contract for man of the match goalkeeper Lucas Covolan and the team declaring that they want to face Manchester City, Manchester United or Liverpool on the road in the next road, it became clear that the celebrations had been going on for some time.
O'Hara quizzed Fagan on rumours that goalscorer, Lamar Reynolds, was spotted eating a pizza outside of a hotel after the match, leading George Elokobi's number two to hold up a McDonald's cup and say: "This isn't Premier League or Championship refuelling going on on this coach right now - this is your kind of coach, Jamie," as they showed a bottle of Hennessy's whiskey that was being passed around the bus.
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Gabby Agbonlahor then asked if they were due for a hefty bonus as a result of their FA Cup heroics, with Fagan saying: "I've said it this week that we need an agent to negotiate that for us - Gabby, you could be the guy to negotiate for us!"
The Maidstone assistant boss then added: "I know how much he was on when he was at Villa, we need him as our agent!"
But among the celebrations, Fagan also paid tribute to his team's performance, declaring: "It was a decent result.
"We did fancy ourselves a little bit but the boys produced two decent goals - the only two shots I think we had all game, but back of the net, that's all that matters!
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"We did fancy ourselves slightly, we just had to stay in the game. That was the main thing.
"Once we went ahead, it was a lot easier to defend.
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"We said to the boys at half-time that if they score after half-time then stick to the script and listen, we won the game. That's all that matters."
Maidstone could have some fuzzy heads by the time the FA Cup fifth round draw is made on Sunday afternoon, but with the prospect of a glamour tie on the horizon, they'll undoubtedly be keenly tuning in to see where their adventure takes them next.