So basically a villain wants humans in Equestria for something and you need a method of how they wind up in Equestria in a non-accidental manner.
Then have said villain abduct them in a manner related to who they are. For example:
The two get meets someone and after some time getting to know each other the person asks them to come with him/her somewhere. Only to be lead into a trap were the person and sone others who were there burst into green flames and turn into changelings. They are then bound in a green cocoon and sent to Queen Chrysallis~
If its Sombra then while the two were walking at a park/alley, with no other people in sight, a black cloud quickly engulfs them and the next thing they know they are somewhere extremely cold and strangely more colorful than usual.
... typing on a phone is hard xp.