The actress, 38, caught up with Fallon, 40, about the season three return of her Emmy-nominated show The Americans, but took a break from the chatting to play a round of the so-called "Inflatable Flip Cup."
Wearing a red suit to match the color of her plastic cups, Russell stood opposite Fallon, who was sporting an equally voluminous puffed-up bodysuit.
"The game is simple," the Tonight Show star began. "We each have six cups, first to chug the beer and flip all of their six cups upside down, wins. We're doing all of this in these inflatable suits. These are great!"
Fallon and the Felicity alum then took advantage of their goofy getups, breaking it down to a beat from house band The Roots.
Once she got the dancing out of her system, Russell faced off against Fallon, admitting that that she had never played a game of flip cup before. While the star's iconic character Felicity Porter attended the fictional University of New York, Russell (an actress since her childhood days on the Mickey Mouse Club) never made it to the flip-cup mecca known as college.
Despite her inexperience with the game, Russell held her own, giving Fallon a tough battle. See who came out on top in the video above!