Tobin "Toby" Seville is Dave's childish and work-shy cousin and The Chipmunks' other caretaker. He is a slacker who loves to play video games. He filled in as caretaker for his injured grandmother, Jackie, whom he was living with at the time while she was incapacitated.
Dave is seriously injured in a benefit concert as a result of Alvin being carried away and knocking a giant Alvin billboard into Dave, sending him flying a good distance. Dave survives the accident but is left temporarily disabled as a result. During his recovery, Dave reveals that he has arranged for them to go to school and for Jackie to watch after him during his recovery. When Toby arrives to take care of the chipmunks he is depicted as lazy, and having a love for video games as well as having a sarcastic demeanor. It is hinted through movie clips that Toby is having trouble controlling them and is often quarreling with the Chipmunks. For example, while playing Wii Bowling, Alvin breaks Dave's new T.V., and a nervous Alvin suggests they play his second favorite game, which is to hide the broken TV. Much to the shock and disbelief of the Chipmunks, Toby claimed he was extremely popular when he went to school. In the flashback he was an outsider and got picked on in high school like Simon and Theodore. He is countered by the Chipmunks who point out that he is still living with his grandmother.
During The Chipmunks' performance in the Squeakquel, he runs into Julie. He nervously holds out his hand for a handshake, but she instead warmly embraces him, beginning a romantic relationship. He is last seen dancing in the finale to "Shake Your Groove Thing" with everyone else.
It's presumed that he went back home to Aunt Jackie's house once Dave returned.
- He is the main (live-action) protagonist in the film, serving as a replacement for Jason Lee.
- He refers to himself as the Tobester.
- In a flashback, Toby appears to be tormented by bullies when he was a teenager at the same high school where the Chipmunks go. He had his face dumped in a toilet, and was pinched by people because of a paper that said “PINCH ME!” which he didn’t notice.
- Before he met The Chipmunks, he mentioned that he had a pet cat, who later ran away, and had became a stray that hates him.
- Toby is portrayed as an "Alvin Super Fan" on the Alvin and the Chipmunks: The Squeakquel bonus features "Squeak Along" DVD. Whenever he is shown talking, his name appears at the bottom of the screen with an animated Alvin and "Alvin Super Fan" tagged along behind it. This would contradict the film as Toby doesn't mention that he is an Alvin fan in the sequel at all.
- Toby’s high school crush was Julie Ortega.