The show, which launched last night (January 31), is bringing back former pop groups from the '90s and early '00s to resolve their differences and perform again. Next week's episode will focus on boyband 911 and Liverpudlian trio Atomic Kitten.
[Atomic Kitten in 2013]
Band members Kerry Katona, Natasha Hamilton and Liz McClarnon admit that they often had screaming matches behind the scenes and that there was lingering tension between Hamilton and McClarnon.
Speaking about a row after a gig at G-A-Y, Hamilton said: "It got more and more angry to a point where we were literally screaming at each other."
McLarnon added: "She just launched at me. You know when you go, 'What the hell just happened?'"
[ITV2's Big Reunion]
The trio also reveal that one of their biggest fights came when Kerry Katona insisted on bringing her popstar boyfriend Brian McFadden on tour, meaning that there wasn't room for McClarnon's younger brother Joe in the car.
"I didn't know she (Kerry) was bringing Brian with her for the day, I'd cleared it with the tour manager that I could bring my little brother," said McClarnon.
"As Brian was already in the car the main thing was that Joe was not going to be able to get in the car so that really, really, really annoyed me... I hit her."
Watch Digital Spy's interviews with the Big Reunion bands:
Katona continues: "Well that was it. I undid my seatbelt, I've gone for her. I kicked her out the car. I said, 'Drive off'. I left her in the street. I was screaming, I was so angry. [After that] I used to make her get changed in the toilets. On stage, I'd stamp on her foot."
Hamilton added: "That fight really ruined their relationship. It didn't end on a good note for them at all."
The Big Reunion continues on Thursday nights at 9pm on ITV2.
Watch Atomic Kitten's 'I Want Your Love' video: