Two Australians sang their hearts out to loud applause in the Eurovision grand final only to see the trophy go to Portugal, while a “pretend” Australian drew gasps by storming the stage and baring his backside to the watching world.

Draped in an Australian flag, Ukrainian journalist and serial prankster Vitalii Sediuk dropped his strides while prancing around last year’s Eurovision winner, Jamala, as she sang during the competition’s half-time break.

Unaware that Sediuk is not Australian and had simply grabbed the nearest flag before jumping onto the stage, many Twitter users wondered if the cheeky incident would hamper Australia’s chances for a return invitation to the competition.

Others rated the incident the show’s winning highlight, with British comedian Dawn French tweeting: “Actually, no…my money now on that bottom!!!!!!! #eurovision”

Sediuk is well known in his homeland for inserting himself into red-carpet spectacles and, most recently, attempting to plant a kiss on Kim Kardashian’s bottom.

Australia’s official representative, Isaiah Firebrace, was joined by compatriot Anja Nissen, who competed on behalf of Denmark in the notoriously over-the-top song contest, which was broadcast live on SBS from 5am on Sunday (AEST).

Portugal’s Salvador Sobral jumped to an early lead in voting and stayed ahead throughout the process to claim his country’s first-ever Eurovision win.

Firebrace ran a creditable ninth while Nissen, who delivered a powerhouse performance of the ballad Where I Am, managed 77 votes to finish well down the listin twentieth place.

Wearing a long flowing red dress, The Voice Australia winner was the picture of confidence as she performed in front of a 50-second cascade of fireworks, the longest pyrotechnic display in Eurovision history.

Portugal’s Salvador accepts the winner’s crystal microphone from last year’s winner, Jamala.

The night’s often bizarre highlights included enthusiastic yodellers from Romania, a boy band in Hawaiian shirts from Spain and a man in a gorilla suit from Italy, but it was the flag-draped flasher who lifted the night from kitsch to controversial.

While audience response was positive for both Nissen and Firebrace, who competed against 24 other countries on Saturday night (Kiev time), the bearded and bespectacled stage invader had many social media commentators wondering why Australia was even in the competition.

The 21-year-old Nissen, whose parents emigrated from Denmark before she was born, rose to fame after winning the third season of The Voice Australia. She stormed through to the finals in Ukraine with Where I Am, a ballad she co-wrote.

Nissen, who grew up in Sydney’s Blue Mountains, had hoped she could rally support from both Australia and Denmark, only to see Australia’s 12 votes given to Britain.

Anja Nissen hits a high note with her song Where I Am

Seventeen-year-old Firebrace survived the first semi-final on Friday (AEST), singing his song Don’t Come Easy.

Firebrace – also a reality TV star, having won last year’s X Factor Australia – was one of the youngest in the competition, along with Belgium’s entrant, who is also 17.

The odds-on favourite had been Italy’s entrant Francesco Gabbani, whose Occidental Karma is already a huge hit in his home country. Quirky as that song may be, many viewers were mystified by his decision to share the stage with a man costumed as a gorilla.

Regardless of the result – Firebrace is already a winner, according to some Eurovision fans, thanks to his most prominent facial feature.

“Australia’s Isaiah wins for best eyebrows,” on Twitter user commented, echoing the sentiments of thousands of others celebrating the teenager’s “earnest eyebrows”.

Isaiah's eyebrow choreography = 12 points #AUS #SBSEurovision

— Angie 🇦🇺 🇲🇹 (@a_bedderz) May 12, 2017

The final also reflected Britain’s post-Brexit disengagement from Europe, with a majority of voters telling pollsters they would be happy to see their country withdraw from the annual contest.

According to YouGov’s survey, 56 per cent of Britons want out. Of those who tuned in to the finals, a quarter said their interest was limited to making fun of the event.

Portugal was the hands-down winner.

-with AAP and ABC