All of the episodes are pretty good, but I really enjoyed a few more than the rest. Trash Boat is where Rigby gets tired of his name and changes it to something that he thinks is more novel and original. When everyone else thinks his new name is ridiculous, he's got to find a way to raise the money to change it back... and his life just might depend on it. Eggscellent is all about one of those timed food challenges at a restaurant. When Rigby fails to eat the enormous omelette within the time limit and, thanks to his allergy to eggs, winds up in the hospital, Mordecai promises him that he will win him that trucker hat, leading to a Rocky-like training sequence and a great Indiana Jones reference. And you can't miss Muscle Mentor, where Rigby comes that close to losing his job and, instead, is mentored by Muscle Man for an entire day. His most difficult task will be to keep from giving up. Or, for that matter, Rap it Up, where Pops decides to join in the fun by taking on a rap crew that has rap battles in the park. Be prepared, however, as Pops is only in it for the appreciation (and power) of poetry - he doesn't want to say anything negative.
The Characters Come to Life: Live Episode Read was actually quite cool, watching the actors-behind-the-characters as they performed lines with the video playing behind them on stage. Another thing that I enjoyed from the special features was J.G.'s explanation of why the Regular Show is called the Regular Show. I always thought the name was stupid and that it didn't apply to the show at all, but after hearing his explanation, I can accept it.
The only complaint I have about Regular Show: The Third Season would really be the fact that it's not on Blu-Ray. I feel that the art style would pop more in high definition, but alas, a Blu-ray version isn't available. Still, it looks good for DVD.
If you like Regular Show and don't have any of the Third Season yet, then I highly suggest The Complete Third Season. If you have some of the themed collections that include episodes from the third season, then you may want to sell them, trade them or gift them to a friend and upgrade to The Complete Third Season; you don't have to pick and choose episodes from this season - they're all entertaining.