(NBC) — NBC’s “Chicago” dramas are all new Wednesday and on “Chicago Fire,”

there is a new chief shaking things up. Dermot Mulroney plays the newcomer and

talked about what surprises viewers can expect this season at Firehouse 51.

The biggest change came last week when Mulroney arrived as Chief Dom Pascal.

“I’ve got big shoes to fill in the storyline and in real life,” said Mulroney. “This cast has been incredibly welcoming, but it’s definitely not the same chief in town, so everybody’s adjusting.”

The firefighters are not quite sure what to make of the new boss.

“They’re not resisting him, but there’s a little griping going on behind his back,” said Mulroney.

So, Mulroney’s character has got some work to do with his staff.

“As far as Stella’s concerned, yes,” said actress Miranda Rae Mayo, who plays Lieutenant Stella Kidd. “They’re bumpin’ heads, which has been fun to play.”

Mulroney’s fit with the cast has been a lot smoother.

“He’s just so kind and humble, such a professional,” said actress Hanako Greensmith, who plays Violet Mikami, a paramedic. “It’s fun seeing him play his character, which is quite different to who he is in person and seeing the contrast on and off set.”

The onset action has been the eye-opener for the new guy watching the show’s stunt crew.

“Really complicated stuff being done like it’s a walk in the park,” said Mulroney. “It’s really incredible to behold.”