With the pressures of high school in their near future, CJ and her two best friends decide to embark on a series of middle school adventures while they can still take risks and have fun.
CJ, Fen and Crispo start a garage band with hopes of winning top prize at the school's music festival. But when creative differences break up the band, CJ must find a way to reunite the team in time for their big performance.
The gang each sets out to conquer their fears, but when CJ is faced with talking to her 8th grade crush, she needs the help of Fenwick & Crispo to cross this item off the list.
CJ notices how many times Fenwick says the word "no" so she convinces the guys to say yes for the day. But while agreeing to everything that is asked of you opens new doors, it also creates unanticipated problems.
The group decides to enter the science fair, but CJ cannot figure out what she wants to do and starts losing her spirit; however, Ronbie raises her spirits back up with a pep talk. Meanwhile, Fenwick builds a robot that is beaten by Mindy's better robot. Crispo tries multiple things to impress one of the judges, but repeatedly fails. Eventually, CJ figures out that she can enter her list of 100 things to do before high school because of the science of whether or not things on the list prepare someone for high school and Fenwick builds a robot that highly surpasses Mindy's, but it goes haywire and wrecks everyone's science fair projects, except Crispo's, whose science fair project ended up being himself because of what his body can do.
When Crispo joins the Save the Baboons club, which is ran by Mindy and Blake, CJ and Fenwick, who were not allowed to join, try to find their own clubs. Fenwick joins the Super Genius club and CJ joins the Club club, which is boring. CJ and the other club members attempt to make it cooler, but it gets taken over by Mindy and Blake's club, so CJ tries one more time in a bigger room. When Crispo discovers that the money donations for the Save the Baboons club is going toward the club's expenses rather than saving the baboons, he leaves and join CJ's Club Awesome club, which becomes a huge success. However, it becomes too much of a success after Mindy's not able to go in, despite everyone being able to join, and CJ, Fenwick, and Crispo not even being allowed to go back in due to the club reaching capacity.
Due to a bad childhood experience, Principal Hader cancels the Halloween carnival. CJ, Fenwick, and Crispo make it their thing to figure out why Principal Hader hates Halloween and fix it. Meanwhile, Crispo is made fun of for wearing what others perceive as a costume for little children. He then changes to a more dark costume to be cool, but later realizes that he should not change simply because somebody doesn't like a particular feature about him.
CJ, Fenwick, and Crispo are all sick; CJ and Fenwick are both home while Crispo wants to know what it's like to have a sick day, but his parents don't ever allow him to stay home, no matter how sick he is. Meanwhile, to keep his perfect attendance record, Fenwick has Crispo walk around with Fenwick on an iPad. Later, Fenwick gives Crispo the idea to get on a bike and go over to CJ's house to make the best of his sick day, but when Crispo gets over there, CJ's not there because she came back to school since she was feeling a lot better thanks to some disgusting green liquid medicine her parents forced her to take earlier.
When a simple lie morphs into an out of control event, CJ and the boys discover the power of words and the messy business surrounding lies, truths and the consequences of telling both.
Crispo attempts to overcome his fear of asking for help in class; CJ volunteers to escort fifth grade students through the school; Fenwick tries to become the high five king of middle school.
