Simon Seville is the middle child of the three Seville siblings (consists of his older brother Alvin and his younger brother Theodore), being the second born and also the second eldest in the family. He is the adoptive middle son of Dave Seville and the biological middle son of Vinny. Like his older brother, Alvin, he was also suspicious of Mr. Talbot's intentions in Alvin and the Chipmunks: Meet the Wolf Man when he and Alvin were invited to his house. In Alvin and the Chipmunks 2: Los Angeles Chinatown Wars, he joined forces with Alvin, Odious (Gregg Berger), and Brittany during their battles against Ho Chan (James Hong) and the Purple Dragons. He wears a blue sweater as his iconic color. In Alvin and the Chipmunks 2: Chasing Camille Leon, when Theodore turned him into a horse, he wears a navy blue feather headdress and navy blue saddle on his back.
Simon is in men's bathroom located inside a fancy hotel in Las Veges, He is shown fixing his blue bow tie when all of sudden, Black Knight (Jennifer Hale) bursts in. She attempted to kick Simon, but Simon dodges her high kick, resulting in Black Knight breaking the bathroom mirror into pieces. A brutal fight between them is heard on the background, but unseen and the force of the blows are enough to destroy another bathroom mirror just outside the men's bathroom. After a while, Simon emerges from the men's bathroom as we see that he has murdered Black Knight in anger and he had used Eleanor Miller's green lipstick to graffiti over Black Knight's face.
- Younger brother of Alvin
- Older brother of Theodore
- Middle son of Vinny.
- Adoptive middle son of Dave Seville
- Boyfriend of Jeanette Miller
- Friend of Brittany and Eleanor
- Protected by Donald Walls from getting killed by Tiger Claw (Eric Bauza), Rahzar (Clancy Brown), Baxter Stockman (Phil LaMarr), Fong (Andrew Kishino), Tsoi (James Sie), Sid (Andrew Kishino), and Fish Face (Christian Lanz) in Alvin and the Chipmunks: Trouble in Las Vegas.
- Other Friend of Kowalski from "The Penguins of Madagascar".