"Unlikely alliance" refers to a situation where two or more people or groups, who are usually different or have opposing interests, come together to work towards a common goal or cause. Full definition
His sculptures combine sound, movement and physics to create unlikely alliances. (imma.ie)
Sometimes, the most unlikely alliances are the most intelligent ones. (entrepreneur.com)
Cargill formed unlikely alliances with Greenpeace, consumers and its competitors to impose a voluntary ban on buying soybeans from newly deforested land. (fooddrink-magazine.com)