The reason they did the merchandising scene in the film was due to an agreement Mel Brooks had with George Lucas that he could poke fun at Star Wars and even use some of its footage (escape pod scene springs to mind) on the promise that there would be no Spaceballs merchandise on sale after the films release. Mel decided to have a giggle at the request and made the scene we all know, happen. He did keep his word though, and did not allow the release of any official Spaceballs merchandise.