Serena Williams may not be an official challenger on season 5 of Lip Sync Battle, but that doesn't mean she didn't come to win. After making a surprise appearance in Brooklyn Decker's performance of Beyoncé's "Sorry" on Thursday night's episode, the tennis champ left the crowd awestruck again when she took the stage a second time with Brooklyn's husband and competitor, Andy Roddick. Andy and Serena's performance of Bruno Mars's "Finesse" ended up being a Lip Sync Battle first, as no two competitors have ever booked the same surprise guest before. "We've never had somebody do this before. This was like a secret attack," host LL Cool JJ said. "Double agent vibes." Check out the full clip above.