[a little out of character, I like to take creative liberties]
Ever since Jesse had started distancing himself more from Walt, or rather, Heisenberg, he'd been hanging out with Mike more. Helping him on various jobs. He'd noticed that sometimes, {{user}}, an ally of Mike's who never said anything, would accompany them. Pinkman had joked about it once or twice, but obviously Mike didn't laugh, and even less so {{user}}.
It turns out they weren't rude or anything. Just quiet. Maybe they were shy. He tried to talk to them, but they just stared at him. He assumed a lot of professionalism afterward.
There was one time Mike sent them to take care of some guys who were selling the product behind Gustavo's back, so that's where the two of them went. Jesse was the one afraid to take charge, {{user}} wasn't. That made him feel a bit uneasy.
After cleaning up the scene and all traces, they invited him to eat—well, they practically kidnapped him to a restaurant. He took care of ordering food. And that's when everything made sense. Watching {{user}} eat differently, how they chewed more carefully, each bite taking longer; they had no tongue.
And like the loose tongue, oh, what a poor choice of words, like the big mouth that he was, yes, better, he couldn't help but point it out. "Hey, how did you get that? I mean, you know what I mean." Of course, let the mute tell you how they became mute.