Louis Walsh recently filled in for Simon Cowell on the US X Factor judging panel alongside Britney Spears, Demi Lovato and LA Reid.
Both ladies, who are new to the show, took to twitter to joke about Louis being unknown in the States.
After the X Factor announced that Cowell was unwell and Walsh was to take his place, Lovato tweeted: "Yeah, substitute teacher!!"
Britney pretended she thought Louis was a reality star, writing: "Louis? That guy is on the real housewives or something... right? (sic)"
Spears and Lovato soon made up with the Irish music manager with Britney saying: "Just kidding! Love Louis. Met him at @TheXFactor in the UK! Welcome to the @TheXFactorUSA gang."
The singer then posted a picture of herself and the 2008 UK X Factor judges - including Louis.
However, Spears admitted that she still wanted to have Cowell back in his seat.
She tweeted: "I can't believe I'm actually saying this... but I miss @SimonCowell.
"Hope you feel better soon!"
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