Cena accompanied Nikki to the Bellas' ten-year high school reunion (I'm assuming Daniel Bryan went, too, because he and Brie are in a relationship); this coupled with Nikki saying that she spent some time in Boston recently helps the argument.
There's also this:
I just wanted to post this because John looks like someone is off-camera with a puppet on their hand saying "look at the birdie!" and John's all "W-birdie? Where?"