We predict the top 5 songs most likely to score a place in Triple J's 2019 Hottest 100.

Billie Eilish has won the 2020 triple j Hottest 100 with her hit song bad guy.

Predictions for the Hottest 100 winner have been upset this year, with numerous betting agencies favourites being knocked over as an unexpected winner streaked ahead this year.

Backers including Betfair indicated Aussie artist Tones and I was a sure bet to take out the top spot this year, but young artist Billie Eilish managed to take out the winning position for 2020.

It’s hard to imagine a world where Eilish’s bad guy isn’t an enormous worldwide hit.

But when Eilish and her brother Finneas O’Connell were writing the song, the 18-year-old star thought it would “flop” for a technicality in the chorus.

Explaining to Billboard that she and Finneas anguished over the chorus during the writing process, trying to come up with something to fill the unusual, lyric-less chorus, the star eventually resigned herself to the fact that the song probably wouldn’t take off.

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Of course – Eilish was wrong, and it went on to be a huge commercial success, reaching number one on the US Billboard Hot 100, as well as the charts in Australia, Canada, Estonia, Finland, Greece, Hungary, Iceland, New Zealand, Norway and Russia.

It was the fifth single from Eilish’s debut studio album W hen We All Fall Asleep, Where Do We Go? released on March 29, 2019

In the United States, Bad Guy ended the record-breaking 19-week run of Old Town Road by Lil Nas X featuring Billy Ray Cyrus.

It’s also tipped to land a position high up in this weekend’s Hottest 100 countdown, airing on Triple J from 12pm AEDT time on Saturday.

“What’s funny about it is I actually thought it would flop … because the chorus doesn’t have a hook – at least what we wrote as the chorus,” Eilish told Billboard.

“My brother and I actually sat in his room trying to write something else over that, but we couldn’t do it because nothing else worked. (We didn’t) want it to be empty there, but we were just like, ‘I don’t know if anyone’s going to like this, because there’s no lyrics here.’”

She went on to say she was “so proud” of the song, adding that it’s her favourite to perform.

“For some reason, people do like it and it’s huge now. It’s one of my favourite songs I’ve ever made. It’s my favourite to perform, it’s so fun. I’m so proud of that song.”

But that’s not the only unlikely titbit from the creation of Bad Guy.

In a video interview with Rolling Stone in December last year, the teenage hit maker revealed that a distinctive Australian sound played an instrumental part in her massive No. 1 hit.

She said she was inspired to record the sound during a visit to Sydney two years ago.

The then 15-year-old pop star was in Australia for Laneway Festival and found herself waiting at a traffic light for a pedestrian crossing.

“My mum and I went for a walk in Sydney,” the US singer explained.

“(When) you press it, it’s like ‘doop doop’. That’s the sound that it makes when you have to wait.”

It’s a sound all Sydneysiders are familiar with as you wait for the green man.

Baffled by what she was hearing, Eilish recorded the sound on her phone.

Weeks later, she was looking through her voice memos and stumbled across the recording.

“We call that sound ‘grart’,” her brother-producer Finneas said in the video, causing the siblings to laugh.

Eilish later admitted the chorus instrumental hook – the same section of the song she thought would make it “flop” – borrowed heavily from the music of video game Plants vs. Zombies and the theme tune to Disney kids show Wizards of Waverly Place.

“It’s not at all the same melodies but it’s literally Plants vs. Zombies … and Wizards of Waverly Place,” she said.

And as for the lyrics?

Eilish says they’re about people pretending to be something they’re not.

“If you’re going around all the time saying like, ‘Yeah, I’m bad, I’m always breaking rules, and doing this and doing that.’ You’re not. I know that because I used to say that and I wasn’t. Bad kids, bad boys, bad b**ches, whatever, they do that sh*t and they don’t even know.”

Triple J’s Hottest 100 starts Saturday from 12pm AEDT