Such an accolade naturally amplified pressure to deliver incredible music for the sequel - right?
"Um, yes," he laughs, adding that the Oscar sits on his piano at home in Wellington and recalling nervous glances at the gold statue, wondering if his work was good enough.
"But then I moved to LA, hired a space on Hollywood Boulevard and put a piano in there. It was this dusty old shop to hide away and work on the songs, but people would be walking by hearing me hitting the piano and come in asking if there were music lessons or if I was part of some art installation."
Once settled in LA, McKenzie, 37, stopped thinking about the award and got stuck into writing tracks for the film, which follows the Muppets as they head out on tour, playing sell-out shows in Berlin, Madrid and London.
Mayhem ensues when the "World's Number One Criminal" Constantine - who happens to be Kermit's doppelganger - and his sidekick Dominic (Ricky Gervais) entangle the clan in their global crime caper.
The filmmakers were flooded with celebrities wanting to join the sequel and everyone from Usher and Lady Gaga to Celine Dion and Christoph Waltz make appearances.
While penning the ballad Something So Right for Miss Piggy and Dion - whose vocals were recorded in Las Vegas then emailed to McKenzie - was "a dream come true", working with the film's leading stars was also a highlight.
"Ricky's one of my heroes. A lot of people don't know this, but he was a in a band in the 80s so he's an actual singer and he was great in the studio because he's got a John Farnham sound. A big, rock voice.
"Ty [Burrell] I'm a big fan of and Tina Fey was another hero of mine. She's not much of a singer, but she got really into it and did a great job.
"It's a pretty awesome job getting to work with people who I really like."
It wasn't just Hollywood stars getting in on the Muppet action. McKenzie's Flight of the Concords partner Jemaine Clement (who turned down working on the music with McKenzie for the first film) nabbed a role as a prisoner, working closely with Fey's feisty prison guard alter-ego Nadya and taking the lead in the jailbirds' musical number Working in the Coal Mine.
"That was [director] James Bobin's idea," says McKenzie. "They needed another prisoner so they got Jemaine to be a Russian con!"
"We didn't work together much - just a little on the finale."
Though the Grammy-winning
FOTC
pair have long been popular in the States, McKenzie says having "Oscar-winner" on his resume has helped open more doors.
McKenzie is also working on a "Labyrinth-style fairytale musical comedy," which he envisions filming in NZ, but for now half of his time is spent in the US.
Wife Hannah Clarke visits frequently with their children, Vita, four and Leo, three, who "literally think I work with Kermit the Frog".
He smiles recalling the duo singing along to songs he wrote for the film, but says he doesn't see the movies as children's films.
"I don't feel like I'm making kids' films. I know that it's family-friendly, but I just do what I find funny and I honestly believe it translates to children.
"There's no need to patronise them by thinking, 'Ok, the kids will like this joke', because kids find things funny that they might not understand. They find the same things funny that adults do by the way people deliver and by people's expressions.
"That's the great thing about Henson's work. He didn't ever play down to children. They just did what they found funny, so the Muppets play amazingly to both adults and kids."
Who: Bret McKenzie, returning to his Muppets composer role
What: Muppets Most Wanted
When: Opens April 10
- TimeOut
