Inept Talent Show Contestant

A character or a collection of characters decide, ill-advisedly, to enter a song contest or talent show (in a Britcom, usually the Eurovision Song Contest or a ripoff thereof) despite the fact that Fred can't sing, Bill can't write songs and John can't play the ukelele. He, she, or they will either:

Fail to win, in the most excruciating and humiliating way imaginable
Appear to fail to win in the most excruciating and humiliating way imaginable, and then come in first place.

Examples of Inept Talent Show Contestant include:

Live Action TV

Previously named for comedy The High Life, where the characters perform a song called "Pif Paf Pof".
Father Ted did this too, with "My Lovely Horse". Notably, done specifically to lose the contest for Ireland, which is tired of hosting.
Monty Python's Flying Circus: the winning entry from Monaco in the Eurovision Song Contest is a nonsensical ditty called "Bing Tiddle Tiddle Bong".
In Scrubs, the Janitor told Elliot he was part of an a capella band, and that it was the best employee band in the hospital. This angered Ted's band who challenged him to a showdown. The result was that Elliot said they were both really good.
In the "Hype Pressure" episode of The Goodies, Graeme and Bill form a folk duo called 'the Twofolk'. They appear on Tim's cruel talent show 'New Faeces' and perform a hideous song called "The World Is Full Of Women and Men". Despite being booed by the audience, they are a hit with the supposedly unscrupulous panelists, who admire the song's naivety and purity. Tim's theatre of cruelty series is cancelled as a result.
Carol Burnette, as her "Eunice" character, has a spot on The Gong Show and is so convinced that her singing talent will be her ticket away from her family that she does a lot of bridge-burning before the show. Bad idea.
The entire premise of The Gong Show.

Web Original

Remember "Elektronik Supersonik", one of the Internet's first Viral Videos from the pre-YouTube era? What you might not know is that it was a tie-in with an entire Borat-esque mythos about the fictional Ruritanian nation of Molvanîa, and was, In-Universe, the country's entry in the 2004 Eurovision Song Contest. Or that they also made a follow-up entry in 2005, "I Am the Anti-Pope".

Western Animation

Also done in an episode of The Fairly OddParents, where Timmy's homemade, crappy film is recognized as a great comedy (though it wasn't intended as such).
In Family Guy, Peter and Lois formed a hippie-esque folk duo, A Handful of Peter, when they were younger and decide to revive it for a talent show. The problem being that that they get stoned out of their minds because they don't think they're creative without it. At the talent show they perform a song called "In God's Eyes We Are All Hot", but afterwards we learn that they lost, and we see that their actual performance was nothing but atonal screaming.
Ron Stoppable in Kim Possible's talent show episode showcases a lot of unusual if not low quality talents, especially compared to Bonnie's amazing ballet but somehow wins.
In the My Little Pony Friendship Is Magic episode "Show Stoppers", the Cutie Mark Crusaders enter a talent show hoping to find their cutie marks. Their performance is a complete disaster (the set literally collapses around them). They end up winning first prize...for best comedy act.