Man, Meta Knight and Marth are both so slick, aren’t they?
The story in The Subspace Emissary unfolds with virtually no dialogue. Every so often you might hear a character yell out their trademark battle cry for a particular special move, but for the most part, things move along at a good clip unaided by voiced lines. (I used a similar technique in the Kirby animated series as well.)
During the story, some characters are (or at least appear to be) familiar with some of the other personalities that appear along the way. However, there are several characters that will treat each other as complete strangers at first, just like Marth and Meta Knight did in the movie above.
What spurred these two, who had formerly viewed each other as enemies, to band together? It’s because they realize now that they are united against common enemies known as the Subspace Army.
Now I know some will think, "Well, duh! Marth and Meta Knight would know that at a glance! Neither of them looks like a Primid!" But look at Wario and Bowser. Both of them are residents of "this world" and yet they are on the side of the Subspace Army.
While members of the Subspace Army are easy enough to spot at a glance, figuring out who’s an enemy and who’s an ally is much harder with other characters. My advice is to remember that old saying: The enemy of my enemy is my friend.
...That said, there is one character who has a rather unusual method by which they can distinguish friend from foe...