It’s not surprising that Wyatt Cenac has been added to the regular cast of The Daily Show. His first appearance on the show earlier this month, as a guy who was bored with the Democratic primary and found the plot twists on Lost much more entertaining, was really funny; he also did another spot a little later parodying Kanye West (with whom he worked in an HBO special). Those appearances were his “tryout” appearances, a test to see whether he would work as a regular correspondent; he did work, and he has the job. Cenac has been on most people’s young-comedians-to-watch list for years, and he also wrote several episodes of King of the Hill (remember the one Bill pretends to be gay so he can become a successful hairdresser? That was his). Sometimes the tryouts last longer than that; Aasif Mandvi was an occasional contributor for almost a year before he became a regular.
But many times when TDS tries out a new comedian, he doesn’t work out very well and either appears infrequently or is not invited back. Wikipedia has a handy list of Daily Show correspondents, but somehow I feel like there have been more; I can’t remember names right now, but it seems to me that there have been a few people who were on once or twice and then vanished. Of course appearances can be deceiving. I could have sworn that Dan Bakkedahl was only on a few times, but actually he was on the show for two years. The reason it doesn’t seem that way is that he never really established a character, and so every time he appeared the reaction was “Who is this new guy?” (To make matters worse, he came on the show just after Stephen Colbert left. Those are impossibly big shoes, not to mention glasses, to fill.)
The great Buck Henry appeared twice in 2007 and it seemed like they were going to give him a regular segment, but he hasn’t been back since as far as I know. I don’t know if it’s just a matter of his schedule, or if it was that the segment itself didn’t work out; his timing didn’t seem to mesh with Stewart’s and the segments were never as funny as they should have been.
For an example of a correspondent who didn’t work out, there’s always Lauren Weedman, who wrote an only semi-comprehensible rant about her year at The Daily Show. And yet I always sort of think of her as a regular, because she was on the show when I first started watching it.