First of all, the thing that stood out the most for me from this pack and, quite frankly, came as a complete surprise to me is that Rigby has a little brother, Don. Don is an accountant, drives a red Corvette and, looks just like Rigby. Well, when he's in his Corvette, anyway. It seems Rigby and Don have been a bit at odds with each other growing up, but Don is oblivious to it. In the episode entitled "Don," we meet Don and find out their story. Don shows up again in "Bank Shot" - which can be confusing if you watch the episodes in the order they appear on the disc. I suggest watching "Don" first, then "Bank Shot" and the rest of the episodes. If Don isn't what you thought Rigby's brother might look like, check out "Temp Check," where Rigby hires someone to do his job, an they end up trying to steal his identity.
Some of the episodes are extremely Rigbytastic, obviously "Don", "Bankshot" and "Temp Check", but also "Rigby in the Sky with Burrito," where Rigby tries a last ditch effort to cross something off his epic adventure list before his school reunion; "One Pull Up," where Rigby is just one pull up away from meeting the fitness criteria to remain employed... and it's not going to be easy; "Rigby's Body," where Rigby's poor diet and stubbornness leads to his body running away from home, leaving him somewhat formless and making it more than a little difficult to get around and "Trash Boat," where Rigby decides that if he only changes his name, he can become rich and famous. "The Heart of a Stuntman" has our heroes trying to get their stuntman licenses so little Timmy's birthday party isn't a bust. Mordecai, Rigby, Muscle Man and High-Five Ghost start off at the beginning, but with the famous stuntman, Johnny Crasher (Bobcat Goldthwait) putting them through the ringer, only two make it to the end and earn their certification - and Rigby's one of them, so this episode makes sense to be in the collection, as well. Many of the others, however, are simply a sampling of episodes that feature Rigby and, if you know Regular Show, you know that he's sort of a major character, so most episodes are going to include him.
It's hard to choose one favorite in this group, but "Sandwich of Death" has to be right up there, as does "Journey to the Bottom of the Crash Pit", both of which take our heroes on fairly epic journeys. "The Return of Mordecai and the Rigbys" is also right up there, for the epic music video near the end and the end of the episode, as well.
There are no special features to be found on the Rigby Pack, just sixteen episodes of Rigby goodness and the optional ability to turn on English subtitles. If you're looking for something extra, well, there's nothing (else) to see. Move along.
If you're here for the shows, however, kick back and choose Play All; all of the episodes in Regular Show: Rigby Pack are entertaining, and I actually found myself laughing out loud at certain points. (Quite frequently, as Psibabe noted.) The only hesitation I would have in recommending this to a fan of the Regular Show would be if they are planning on collecting the seasons, because of duplication.