Eric is initially introduced as a new student at Middleton High. He and Kim are immediately attracted to each other, causing Ron to become jealous of their relationship, which also makes him realize that he has feelings for Kim. She and Eric go to their high school prom together, but he's seemingly kidnapped by Drakken and Shego at some point. However, when Kim and Ron go to rescue him, it's revealed that Eric is actually one Drakken's synthodrones (Synthodrone 901, specifically) and that he was just created to bait Kim in.
But, like usual, Kim, Ron and Rufus defeat Drakken and Shego, and Rufus kills Eric by puncturing a hole in his foot, thus leaking his "syntho-ooze." Kim and Ron go back to their high school prom, this time as a couple, and share their first kiss as one during a slow dance to "Could It Be."