Bringing back those two actors -- Kira's friends -- was a masterstroke I'm hesitant to believe the creators of the other series would have seen as much point behind. Of course, it could have just been a matter of convenience, as these things often are.
"Hey, we need to cast for this character, Kira's friend."
"She already has friends."
"Just get one of them."
"We'd need contact info for that. An audition would be easier."
"No. I have the numbers for those two actors from a previous episode right here."
"Well, hell. That saves time. We'll make it two of them, then, and we'll make it them."
Regardless of what happened, it helps tremendously in selling the story. The casual viewer is given enough information to feel something. The regular viewer will go, "oh hell, it's them. They wouldn't... oh, snap, they did."