Paula Abdul
Although this one has never been confirmed by either party, we can see why there could be a rift between Paula Abdul and Ellen DeGeneres. According to sources, Paula never got over the fact that Ellen replaced her as an American Idol judge.

Sure, Paula had her issues as a judge and there were quite a few people who questioned her ability. Having said that, at least she had some singing experience unlike DeGeneres who doesn’t, unless you want to count her dance battles with her audience members. The fact of the matter is, nobody likes being replaced whether it’s a job or a relationship.