Explain how two people of different interests and background could become unlikely allies

Two people who have hated or are completey different from each othe could become allies if they found out they had somethng in common. Having something in common with someone that a first has been the complete opposite of you you to could have a factor that brings the to of you together. Because of that thing that has unites those to people could make them very stronger and become very fast. Not that long ago I personaly saw two different of different races become allies. They were decents of two different races. But a stituation that they faced in the community they went to school in were brought together were brought together to fight a common oppresssor after the fight was down they had become very good friends.