In my headcannon, the MLP ones meet members of the French Foreign Legion.
In Tarzan’s universe, Rainbow meets some including an oppressive lieutenant-colonel known as Staquait (based on the one from The Legend of Tarzan) who poisons her for defiance. And Jane Porter heals her and guides her. And in return, Rainbow saves her and her family from Staquait and a robotic chimera possess by the spirit of the one who fell to her ancestor in the Greek legends. And Staquait is kick out by a lieutenant-general of his legion, and replace by Jane’s virtuous uncle who gets promoted from captain to commandant (their version of a major). And the uncle leads his legion to help the MLP and Tarzan’s jungle; becoming a lieutenant-colonel, then a colonel, then a brigadier-general.
Also I. My headcannon, the MLP ones meet members of the French Foreign Legion in World War 2. And the Gen 5 ones meet descendants of some members spotlight Nazis.

Grand one. And a sheone. Feminism.