Late Night With David Letterman was at the height of its popularity back in the mid '80s, and The Avengers comic book was finding a similar level of success, so a crossover was thought up that saw a number of Earth's Mightiest Heroes appear on the show. However, they were ambushed by a villain who tried to take them out with camera mounted lasers. Letterman would save the day by knocking him out with a giant doorknob. Seriously.