The 'Malcolm in the Middle' star admits to ET that he's afraid his hips won't move when he hits the ballroom Monday night.
ET breaks down everything you need to know about what to expect in the ballroom Monday night!
Backstage at 'DWTS,' Muniz told ET he spends five hours in rehearsals... and SEVEN on various healing remedies for his back injury.
Despite their aches and pains, the stars managed to rule the stage with some impressive performances.
Plus, hear his pro partner, Witney Carson, gush over his work ethic in rehearsals!
ET chatted with Frankie Muniz and dancing partner Witney Carson after their first 'Dancing With the Stars' performance.