The former Parkhead boss was appointed at the City Ground this week and was unveiled in front of the media for the first time this afternoon, ahead of their clash against Arsenal at the weekend.
The press and fans in Scotland, and those from his time at Tottenham, are familiar with the Australian's form during press conferences.
One was on the receiving end of his sharp replies on today.
Postecoglou was ridiculed for guaranteeing he would win a trophy in his second season at Spurs but had the last laugh when lifting the Europa League – before losing his job anyway for finishing 17th in the Premier League.
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Referencing that, one reporter said: "We know you win trophies in your second season," before Postecoglou jumped in and replied: "I have won a couple in my first (season) as well.
"At Celtic I won a double in my first year, so there you go."
Asked if he could do that once again, he laughed: "Yeah, of course I can.
"I may have to have a second year here, mate!"