I like Mos Def. But I just found that gimmick took away too much from the show. No, it's not the same thing as a musical. But nonetheless it's an "oddity" episode. A "special" of sorts and usually advertised as such. Likewise when some shows do a "Live" episode.

These episodes are usually going against what makes the show good in the first place. If the special is "better," then why not have all episodes following that theme?

It's like putting steak sauce on a good steak. You might as well be dragging it on the floor from the kitchen to the table. Now if you're talking about hamburger....