Islamic law forbids visual depictions of Allah or other significant religious characters such as the prophet Muhammad. The Danish newspaper debacle clearly illustrated the consequence of breaking this tenet, as riots in numerous countries caused significant destruction and, in some cases, death after caricatures of Muhammad appeared in print.
Oddly enough, this response to the cartoons came four months after the initial publication.
The Danish newspaper isn't even the first case of visually illustrating Muhammad in mass media. South Park aired an episode in 2001 entitled Super Best Friends\ that included the Muslim prophet Muhammad as a character.
During the episode, this character had the ability to fly and control fire, and was punched by a giant stone Abraham Lincoln all while participating in a multi-religious super team under the direction of Jesus. After multiple airings in the States and in syndication throughout the world, not even the slightest response has been reported.\