Season 3 had an episode that dealt with religious ‘icons’ in general (called ‘Signs from Heaven’ I believe). Last season (6) had one that really bashed hard Islamic jihadism and people who give it a pass in a ‘World Peace’ episode.
“I’m looking for it in those seasons but I don’t see an entire episoded dedicated to Mohammad/Islam in any season. Which episodes are you speaking of?”
Critics of religion like these guys and Bill Maher tend to be very bold when it comes to attacking religions that won’t fight back, like Catholics, Evangelical Christians and Mormons, but I don’t hear them say nearly as much about Islam.