One of my favorite shows. If you're looking into watching it, you might wanna quit after Season 6 but don't, because Season 7 is a great season in my opinion. Season 8 is good too. The character development is amazing even though there should've been more development on some characters. But if you're looking for a funny show with adult jokes, and also amazing character development and good plots and arcs, then Regular Show is the show for you.
Also just a warning, you will probably cry at the ending.