Simon Seville is the deuteragonist of the series and films. He is the smartest of the group, possessing an I.Q. just north of Einstein.
Simon possesses a very dry sense of humor, as well as a keen wit. Simon gets along great with Jeanette, who is smart, just like him. They are shy about their relationship, however, it is obvious that he cares for her.
Simon is the smart brother of the three and is seen as the person who values the 'status quo' of action, often correcting his brothers or The Chipettes if he perceives them as wrong. He is the middle child, as revealed in the episode Grounded Chipmunk when Alvin states he has "never been alone, except those five minutes before Simon was born." Simon's often seen spending the most time with Theodore and often is working on a science experiment. His eyesight may not be as bad as Jeanette's because he still looks directly at the person he is speaking to and rarely bumps into things with his glasses off, both of which Jeanette does.
Alvin exploits Simon's mastermind (less so than either series), though Simon secretly worries that they share the same gene pool. In Alvin and the Chipmunks, Simon is shown as a little less reserved and with a reduced higher intelligence at times (such as giving Dave a paperclip compass). Despite this, he still corrects Alvin every now and again. His eyesight is so extremely poor as he's unable to see a toaster waffle fall directly in front of him without his glasses.
In Alvin and the Chipmunks: Chipwrecked, Simon has an alternate personality caused by a spider bite. His alternate identity goes by the name Simone, who speaks with a French accent and frequently flirts with Jeanette. Simone is depicted to be braver and less uptight than Simon. Near the end of the movie, Simon recovers from the bite and reverts back to his usual personality.
Simon is once again the brains of the Seville family. He frequently corrects Alvin (such as in Sister Act when Alvin misspells "in" as "inn") and uses his technical abilities to help improve his standard of living (rewiring a talking teddy bear in Talking Teddy or building a robot bodyguard in Bully For You). He retains his dry sense of humor and sardonic quips while frequently replying in intellectual stammer (Clowning Around) or covering his ears (A Is For Alien) when he disagrees with something Alvin plans to do or say. Simon isn't afraid to stand up for what is right (Simon For President), though he slips on his duty sometimes (such as in To Serve And Protect) but ultimately takes the responsible action nevertheless. When Simon is pushed by the stress he has moments in which he suddenly snaps at others (For Whom the Bell Tolls). Simon, on multiple occasions, sleep-talks allowing Alvin to easily manipulate him (Jeanette's Secret Garden).
Simon is commonly seen wearing a dark blue top and a pair of glasses. He is the tallest chipmunk, even slightly taller than Jeanette.
Before The Alvin Show, Simon wore a red vest with an S on it and didn't wear any glasses. After The Alvin Show was created, Simon was given more human features, and instead of a red vest Simon began wearing a blue sweater, black glasses with light gray lenses, and black shoes.
In Chipmunk Punk, Simon's hair is spiky as if he were a rock star. He once again wears his black glasses, blue sweater, and all black shoes to match the style of the album.
In the Alvin and the Chipmunks series, Simon wears black glasses with white lenses, a blue sweater, and a pair of white and red patterned shoes. As the series progresses, Simon's glasses become blue, though in The Chipmunks Go to the Movies episode Batmunk his glasses are gold.
Simon, in the CGI/live-action films, has dark brown fur and blue eyes. He only wears a blue hoodie and a pair of black glasses that came from a toy Santa Claus. His appearance was modified to look more closely to a real life chipmunk.
In ALVINNN!!! and The Chipmunks, Simon has brown hair and blue eyes. He wears a two-different-shades-of-blue non-hooded sweater, dark blue jeans, white sneakers with two grey stripes and large, blue-rimmed glasses. His pajamas consist of a long sleeved blue t-shirt with a robot on it and light blue and white plaid pants.
Simon and Dave have a close relationship as Dave takes care of him along with his brothers because they are his kids. Dave has confidence in leaving Simon in charge or in Simon's ability to help him with things he's not comfortable with.
Simon and Alvin always seem to be arguing, like when Simon disagrees with one of Alvin's schemes or with how far he takes them. Alvin can be jealous when Simon takes his role as a "heartthrob" with the ladies, but, nevertheless, Alvin is protective of Simon and loves him.
Simon and Theodore also have a really close relationship. Simon always seems to be with Theodore most of the time, Simon is also often seen to be protective of Theodore. However, despite his protection of Theodore he values him just as much as his brother Alvin and foster parent Dave.
Simon and Jeanette have a very strong relationship. During the two series, their relationship can be described as best friends who have secret crushes on one another. Simon is always looking out for Jeanette and stands up for her. Simon seems very protective of Jeanette, and the two of them spend a lot a time together. In My Sister The Weirdo, it is shown that he can be jealous of others helping her instead of asking him. In Big Dreams, they are married in the future.
Simon and Brittany are friends, but they don't interact very often. Brittany interacts more so with Simon in ALVINNN!!!, such as acting as his campaign assistant in Simon For President (helping him appeal better to the general public) and showing tough love in A Room of One's Own to get Simon to admit he misses Alvin.
Simon and Eleanor are friends, but they don't interact very often.
|Simon: Since he feels it's as close to a world trip as he'll ever get. - (The Chipmunk Adventure)|
|Simon: Well, if you insist on going, don't take the easterly route. I heard on the news there's a hurricane coming in that direction! - (The Chipmunk Adventure)|
|Simon: We've got to keep these two apart. - (The Chipmunk Adventure)|
|Simon: Don't tell me what I want Arthur! You're the only man I've ever loved... will ever love! - (Meet Frankenstein)|
|Simon: That little glass of yours is always half full, isn't it? - (Meet Frankenstein)|
|Simon: Given the choice...I'm in. - (Meet the Wolfman)|
|Simon: Well, our lips are moving and words are coming out. - (Alvin and the Chipmunks)|
|Simon: They just did take us alive, Alvin. - (Alvin and the Chipmunks)|
|Simon: Glasses! Glasses! You wouldn't hit a guy with glasses, would you?! - (The Squeakquel)|
|Simon: Her glasses were quite fetching. - (The Squeakquel)|
|Simon: This is not just a spider! That's a phoneutria bahiensis; its bite contains a neurotoxin! - (Chipwrecked)|
|Simon: Jeanette and I are dating?! - (Chipwrecked)|
|Simon: As long as Alvin is around we'll always get into trouble. - (The Road Chip)|
|Simon: Spare me the boo-hoo eyes, Alvin. - (Family Spirit)|
|Simon: I've had enough with all these egotistical unicorns. - (Safety Third)|
|Simon: Unless you put Alvin in a cage, there's always a chance something's gonna happen. - (Special Delivery)|
- The origin of his name comes from Simon Waronker.
- Simon is frequently regarded as the oldest of The Chipmunks given his height and maturity and is often a center of controversy among fans. In the 80s series, however, Alvin is proven to be older than him in the episode Grounded Chipmunk. Simon's age in the CGI/live-action films has never been stated. Though the CGI series' websites in various countries contradict each other, some state he's older than Alvin by eight seconds while others say Simon's younger, the boys' birth order is confirmed in The Sub when Alvin refers to himself as the "middle child."
- Throughout the franchise, Simon has constantly switched between wearing black glasses and blue glasses.