When you have a loyal, cult-like following, one way to perpetuate it into the indefinite future is to make a game out of your product. "Seinfeld" gave us Festivus, Harry Potter gave us Quidditch, Infinite Jest gave us Eschaton, and now it looks like "It's Always Sunny in Philadelpia" has given us CharDee McDennis.
Basically, this episode consisted of the Gang playing this violent drinking game and explaining some of its many, many rules, and little else. That being the case, it doesn't make much sense to provide a synopsis beyond that.
"CharDee McDennis" was a solidly amusing episode with some good character-driven humor, although it loses some points for being ultimately pointless and plotless. The game itself was wildly clever. The characterization was generally spot-on, and it was especially nice to see Mac behaving a bit like Mac again after a few episodes that really didn't seem to know what to do with him. On the other hand, though, I feel like the episode itself wasn't as clever as the game's pure ingenuity. In other words, reading a "How to Play CharDee McDennis" guide might have been more amusing than watching an episode about characters playing the game. It may have been a better idea to reference the game in an episode and publish a how-to-play guide for the fans than to structure a whole episode around it. Overall, though, "CharDee McDennis" was very amusing. There was a relaxed vibe among the cast and, as usual, it was fun to watch the characters being themselves. It wasn't as cleverly plotted or bust-your-gut funny as the show's best (or even the show's typical) episodes, but there wasn't anything *egregiously*wrong with it either (see "Frank's Brother" for an example of several things being egregiously wrong with an episode).
I probably wouldn't even bother writing a review of "CharDee McDennis" if I wasn't somewhat concerned that this show could fall into the trap of becoming too comfortable with the likelihood of repeat viewers tuning in to see characters being themselves and thus too scared to be as daring as it was in previous seasons. "It's Always Sunny in Philadelphia" isn't and should never become "comfort food" for repeat viewers. This episode was strong enough to pacify fans for another week, but I wouldn't sell the show to a potential new fan on the basis of it, and I'm not sure whether fans will stick around if episodes like it become the norm.
Again, though, "CharDee McDennis" was amusing throughout and not nearly as off-putting as "Frank's Brother." It was a slightly below-average "Sunny" episode, which is still pretty damn good.