When Chuckie's biggest competition in the election for School Safety Commissioner is Dil's imaginary alien friend Izzy, you would think he would have it in the bag, right? WRONG! When Izzy becomes more popular than Chuckie, can he even rely on his friends to help him win?

After Stu sells an invention, he tells the kids that he's splurging on a built-in swimming pool. While digging up the yard, the construction crew unearths the Rats' old mechanical Reptar toy. The kids fondly remember it, but decide to throw it away, until, during an electrical storm, they become convinced that they've angered Reptar. They ultimately decide to rescue the toy, and realize that, although they're growing up, they can't forget their past.

When Susie gets chosen to sing at a big parade in New York City, the tweenage Rugrats hit the road with their moms on a cross country trip! Will Betty's clunky old motor home be able to make it to NYC and see all the stops along the way (like the world's biggest ball of yarn)? Will Tommy and his pals go crazy from lack of video games and TV? Will Chuckie finally get kissed?

As Phil and Lil's birthday nears, the twins realize that they are more different from each other than they think. Phil is getting to like girls, and Lil is wearing a pink training bra. After a shocking incident, they decide to have separate parties for the boys and the girls as they try to out-prank each other.

Tommy is getting annoyed by Dil's eccentric behavior, and he wants some space from his little brother. When the gang visits the Cirque Extravaganza Day Camp, Dil meets a whole group of kids who are just as eccentric as heÿis who invite him to join their troupe permanently. Will he choose his new circus friends over Tommy?

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.

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.

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.