Simon Seville is the smartest of the group, possessing an I.Q. just north of Einstein. He is the only original chipmunk in the series known to be bespectacled. He possesses a very dry sense of humor as well as a keen wit. Simon gets on great with Jeanette, one of the The Chipettes, who is smart, just like him. They are shy about their relationship, however it is obvious that he cares for her.
Simon is the Middle child of the three Chipmunks, as revealed to us on the episode "Grounded Chipmunk" when Alvin states he has never been alone, except those five minutes before Simon was born.
Alvin exploits Simon's master mind. In the end, Simon loves Alvin, although he secretly worries that they share the same gene pool. His signature color is blue, and has the same color eyes. He wears black glasses in the live action film. In the 2009 sequel , he was convinced he was given a swirlie by some jocks. After he

and Alvin saw them picking on Theodore, he and Alvin attacked the bullies. Later, he is tricked into thinking that he is the school's litter monitor, only to find it was a joke. Simon has a crush on Jeanette. He holds to be the middle aged chipmunk, although he is taller and more mature than Alvin. He cares deeply for Theodore and Alvin and their well being, but wishes Alvin would act more mature and stand to learn more. He relishes Theodore's good nature but Alvin always takes to taking advantage of Theodore's gullibleness along with the fact that he is young and naive. Alvin tries to usually be the boss of Theodore and Simon. However, in the 2007 film, he seems way more laid back and non controlling but this returns in the 2009 Squeakquel. He cares for Alvin even though they always fight,but he worries if somewhere deep down, they are alike