New to Venture Bros and I have some questions.

A long time ago when this show was fairly new (I think) I saw a couple episodes and kinda wrote it off. From what I saw, the show was about this ex - super scientist and his idiot sons that had a super bad ass bodyguard that protected them from a shitty villain with his hot, but man voiced, girlfriend. The plots seemed over the top and excessive. Well I've been leaving the TV on in the background while I play games on my computer and have caught a few more episodes recently. Tonight I saw the special and it was amazing. Had me hooked the whole time and I barely had any context as to what was going on. So my questions are; at what point did this show become this good? Was it always this good and I just missed something before? Is there a specific season/episodes where the show gets better over-arcing plot between episodes? Is there somewhere I can go to watch episodes online or would I have to buy seasons? 5 seasons seems like a lot to catch up on, but if what I missed was as good as this special, I might just have to make some time for it.