SINGAPORE – Before taking the court at the BNP Paribas WTA Finals Singapore presented by SC Global, we grabbed Sania Mirza, Martina Hingis, Kristina Mladenovic, Carolina Garcia and more doubles partners for a hilarious challenge.

They might be serious competitors on the court, but off of it, who can keep a straight face against their doubles partner in a staring contest?

Check out the video below to find out, and look out for Bethanie Mattek-Sands’ sure-fire strategy for making Lucie Safarova laugh!