Cheryl was supposed to either completely mime or sing along to the backing track in this performance, which unfortunately however never came on leaving her to awkwardly dance and breathe into her mic for the first minute and a half before finally starting to sing live.
Britney Spears- Toxic live Jingle Bell Ball 2003
Britney's platform was temporarily not working leaving her to scream "Go Up!" several times to the stage crew #divaney
Rihanna- Where Have You Been live 777 Tour London 2012
Once again, the backing track was off from Rihanna's vocals and the band itself, leaving BadGalRiri to start it again in the middle.
Britney Spears- Boys live Onyx Hotel Tour Vegas 2004
In Britney's case the backing track never came on, leaving her to have to sing this high-energy number all by herself (shocker!)
Hilarry Duff- Come Clean Live MTV New Year's Eve Show 2004
The track starts skipping at about 2:40 and awkwardness ensues.
Beyonce- Ring the Alarm Live The Beyonce Experience 2006
Beyonce falls down several stairs but recovers like a pro and continues the song as if nothing happened! Despite her best efforts however the clip was soon posted online for everyone to see.
Katy Perry- Roar live 2013 NJR Awards
In a yet unexplained mess, Katy was either supposed to lipsync or someone turned the backing track way too loud for the first performance which then proceeded to slowly break down. Katy was given the chance to re-do it but arguably the result wasn't any better the second time around either.
Selena Gomez- Come and Get It live Jingle Bell Ball 2003
Selena was not only heard saying "what the fuck" before the performance begun, but when it did she was visibly pissed off while also doing a poor job at lipping the song.
Britney Spears- Slave 4 U live The Circus Staring Britney Spears Tour 2009
Don't be so quick to wear leotards y'all! Cause you might risk having your privates exposed to 15,000 people as Britney learnt on her Tampa Circus show
Beyonce- Diva live I Am World Tour 2010
When the light show didn't go on as planned, Sasha fierce continued the show, after proclaiming that someone would get fired! Added especially for ballroom
One Direction- live Scotland
Harry Styles had a powerful moment on stage when a flying show landed directly on his crotch, leaving him to dramatically drop down on the floor.
Resident Mexican Queen Juan Gabriel falling off stage
Our good sis Juan illustrating the dangers of going too hard whilst performing.
Madonna- Where's The Party live Blond Ambition Tour Barcelona 1990
M did not realize that her mic feed was still on after she left her stage, leaving her outbursts being heard by everyone in the stadium.
Britney Spears- House of Blues Tour 2007
Britney had an interesting couple of shows on her 2007 club tour. First, her outfit started falling apart during Slave leaving her to take it off and then run backstage. Then on another show, Britney's backing CD skipped leaving her to ad-lib some live vocals!
Mariah Carey- Collection of interesting on stage ad-libs on GMA 2008 and Today Show 2014
Mariah sure brings a lot of personality on stage! So much so that she likes to add a bit of flavor to her songs by either telling her back-up singers to stop singing her part baybeehh or informing her fans that she's forgetting the lyrics to her songs
Source: Youtube + my abundance of free time