The Irish music mogul struggled to name each individual in the boyband, even though he is their mentor. But, sticking up for Louis, Only The Young's Betsy suggested his lack of memory could be down to stage fright...
During Saturday night's 'Big Band' show, Mel B told Stereo Kicks - who have just celebrated 100 days since forming - she still didn't feel like she knew each individual boy in the band.
From her own experience of being in a girl group, Mel told the eight piece it was important for their individual personalities to shine through, so each member can then be recognisable.
Testing Louis, Simon then asked his fellow judge to name all eight boys. Ater naming just a few, Louis couldn't help but sneak a cheeky look at his notes in front of him...
But, speaking to BANG showbiz, Betsy defended her mentor.
"[Louis] does know our names," she insisted. "I think it's maybe stage fright when he's put on the spot."
Betsy's bandmate Charlie was quick to agree with the blonde singer, claiming he is willing to let Louis off for being a bit forgetful.
He said: "[Louis] actually works really hard... He's got so much going on in that mental Irish brain of his. We'll let him off."
Meanwhile, Only The Young have said they are super-excited to take on this weekend's 'Whitney versus Elton John' theme.
Tweeting from the band's official Twitter account (@OTYOfficial), the group said: "Busy day rehearsing for the weekend ahead! Elton John vs Whitney... Two of our heroes. Excited is an understatement."
Last Saturday on The X Factor, Only The Young impressed the judges with their fun-loving performance of The Jungle Book's 'I Wanna Be Like You'.
While Cheryl Fernandez-Versini told the band they brought the fun factor to the competition, Mel said: "You know what you're doing and you do it really well. I would go to your concert any day!"
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Watch Only The Young's performance of 'I Wanna Be Like You' here: