Kevin Hart and Conan O'Brien both have jokes that could keep us laughing for days, but we don't think Conan was laughing after going head-to-head in the gym with the hilarious, yet incredibly fit Jumanji actor. On Sept. 29, the two comedians worked out their important muscle groups and their witty disses during a skit on Conan's show, but it was all fun and games until Conan needed a boost during pull-ups. "Get under my ass!" he demanded. "A little boost or I won't promote your f*cking movie!" That's all it took to get Kevin under there. They worked out with medicine balls, punching bags, and enlisted some trainers for help, but even they couldn't save Conan. Watch the video and see what happens when two comedians face off in the gym.