Watch All Grown Up! Season 5 in Australia

Tired of being considered a "goody goody" by the popular kids, Susie tries desperately to prove that she can be a bad girl.

When Chuckie discovers that Kimi is upset, he comes to the conclusion that she hates how her room looks. The gang decides to help him redesign it for her while Angelica keeps Kimi busy. Dil tries giving advice, but they choose to ignore him. It is later discovered that she is homesick for Japan and her biological father. Chas and Kira have a big surprise for Kimi.

While the gang try on their Halloween costumes in the Finster's garage, they find TP+KF carved on the wall. Chuckie believes that Tommy has a crush on Kimi. The argument between Tommy and Chuckie escalates to where their friendship falls apart. So the rest of the gang tries to bring the two back together, but backfires. The two eventually make up when Chuckie saves Tommy from the middle school goons who were chasing him.

When a comic book starring Chuckie's favorite superhero Armadillo Dave gets cancelled, he becomes too depressed to help Tommy with his science fair project. Tommy has to buy a rat for his project, but the last rat available is a mean one. It scares everybody. Kimi made Tommy a simple one lane track for his rat, much to his disappointment as he feels he would get a failing grade for it, but needs Chuckie so he can get a good grade on it since Chuckie has done it before. The gang tries to find Chuckie a new hero to worship.

Angelica's teacher is having a baby so she brings in a hot handsome substitute teacher that Angelica falls in love with. She tries to date him by failing her assignments. Meanwhile, Tommy, Phil, and Chuckie are part of the tennis club run by Pangborn. Chuckie is trying to avoid showering at the boys' locker room, but when he takes the chance, he realizes he has nothing to worry about.

Tommy's girlfriend, Rachel is moving away, and he's cool with it, but is not sure why. However, his friends think otherwise, believing him to be in denial. Tommy tries going about his life as normal, but everyone keeps trying to show him compassion, annoying him greatly. Tommy is advised by Dil to go along with the plan so his friends will leave him alone. However, when Tommy hooks up with another girl, the gang unexpectedly have Rachel show up to surprise Tommy. Seeing him with another girl so soon is too much for her to bear, so she walks away again, leaving Tommy to cry for real this time. Chuckie then shows up at Tommy's house to comfort him.

Kimi leads a petition drive to ban cell phones in school. To prevent her from having the cell phones banned, Angelica hoodwinks Chuckie into helping her keep cell phones in school in her petition drive, while Susie helps Kimi counteract. Things get worse when during the debate at a school assembly, Chuckie reveals to the audience that Kimi wants a cell phone for Christmas, and they end up not speaking to each other and threatening not to attend their parents' (Kira and Chas) 10 year wedding anniversary. However, Angelica, Susie, and Tommy force them to attend to attend. At the Java Lava, Chuckie and Kimi argue with each other about cell phones until they make up after Tommy shows a video of their parents' wedding when they were babies.

With Stu and Didi away at an Invention Convention, Dil wants to host a viewing party for a "real" alien autopsy video with Tommy. But when both Grandpa Lou and Grandpa Boris show up to babysit the kids, they all start to have a feud. This gets even more difficult when Phil, Lil, and Chuckie show up and Dil invites 10 other kids to come see it, much to Tommy's frustration.

When Tommy's gang's parents feel that they are spending too much time watching TV, they ban it from the house. So in order to get their televisions back, they do something dare-devilish. They make a tree house with a zip-line in the backyard to scare and anger their parents into giving them their TV back.

In the series finale, When Tommy forgoes going to the traditional opening day ball game outing with his Grandpa in order to patch things up with his former girlfriend Rachel, Lou takes Dil instead. This makes Tommy jealous as he and Dil compete to be Lou's favorite grandson during a fishing trip.