At New York Comic Con, the two artists drew pictures for an auction.
A little awkward for both artists, especially for Jim Lee, but both did admirable work .They loosened up towards the end. All the work was for charity.
Look for the video on Sy Fy channel.
They were not the first however, 46 years ago, Neal Adams, Joe Kubert, and Moebius did the same on the Tac au Tac show---look it up.