What's The Work?
Regular Show is an animated sitcom that centers around Mordecai and Rigby working, a raccoon, who work as groundskeepers at a park while making attempts to avoid work and find entertainment, which leads to bizarre and unexpected situations.
Who's The Character?
Rigby is one of the two main protagonists (alongside Mordecai) of the Cartoon Network TV series Regular Show, and Regular Show: The Movie.
Why He Doesn't Qualify?
One might think Rigby subverted all of his idiotic and incompetent moments throughout the show like Mordecai does and became smarter and more guile over time. Well, there's three big problems with this:
1: It's not confirmed and/or shown that Rigby has subverted any of his acts of idiocy or incompetence because in season 8 of the show, he still didn’t subvert these qualities until at least the season finale, which means it's been debatable if he learned or has grown from his dimwitted behavior, and this doesn't mean he's no longer a dimwit.
2: His series of irredeemably bad decisions he's made just makes him out to be way too reckless and heedless than necessary for a Guile Hero; with episodes like: "Just Set Up The Chairs," having Rigby ignore Skips' note advising them to not connect the red wire to the blue wire (Rigby doing this ends up releasing the Destroyer of Worlds which endangered the park's visitors and killed the special entertainment people), "Diary"; having Rigby disobey Skips telling him and Mordecai to not open their eyes while doing the ritual for Margaret's diary (Rigby not listening to him caused the guardian of Margaret's secrets to attempt destroying them), and even in the movie; not only did he forged Mordecai's rejection letter so he could be with Mordecai forever, which not only set up the upsetting events of the whole series, but he also caused Mr. Ross to become a dangerous villain due to Rigby carelessly ruining a volleyball game Ross put his time and energy into all by Rigby sabotaging a team for no good reason (which turned Ross into a galactic destroyer). Despite Rigby having little remorse for the things he does, he doesn't ever seem to learn or grow from this since he's often too self-centered and arrogant to realize when he's wrong until the very last minute.
3. With that said, he easily fails the guile standards of the series to several heroes in the show like Mordecai; who has used his intellect to destroy the Timenado and reason with Future Mr. Ross to stop him from destructively changing the future, Benson; who used his intellect and wide knowledge to protect his employees many times and managed to maintain the park tidy despite the destruction it has, and even Skips; who managed to solve most of Mordecai and Rigby's problems on his own and used his strategic prowess to do very practical things like using the PlayCo Armboy to defeat Death in a game of arm wrestling and also force Death with the promise of reviving Rigby.
Conclusion?
In my opinion this is a rather easy one and a clear Cut since it's clear that Rigby isn't as smart as Benson, Skips and even Mordecai in the same regard.