The Hollywood star hopped onstage at the Adelphi Theatre and ran through a comedy routine as the crew struggled to fix a screen that had come loose on the set.
DeVito was also joined by Heather Headley, the star of the musical, who led the audience in a sing-along of Happy Birthday for her director, Thea Sharrock, 36.
Sharrock, who previously directed DeVito in the London play The Sunshine Boys, tells London's Evening Standard, ""It was so crazy but what a treat. And then Danny did a little stand-up while we waited. It was a unique night, one of those bonding experiences. The audience were fantastic.""