The Irish duo have been brought back to stand in for Olly Murs, who will miss the audition stages of the contest due to his US tour with One Direction.
Caroline was joined by former X Factor stars JLS on set yesterday, and it's expected that Jedward will join her later on in the audition tour.
Both One Direction and The Wanted are also tipped to appear alongside Caroline, with bosses bringing in boy groups to replace Olly!
A source said: "[Olly] will be back for the live shows but in the meantime we need stand-ins as it’s quite a rowdy show and works better with more than one presenter. It was going to just be JLS before, who have experience of the show as that’s what shot them to fame.
“But during talks we realised that it might be better if we used a few boybands.”
The Xtra Factor returns to ITV2 in the summer.