Legal Question in Real Estate Law in California

This is hard to answer without some idea of why the plaintiff put your name on the Small Claims form. You probably have some connection with the lease, since you know what names are on it. Maybe you are an assignee? Did you buy the business and change the name? Have you paid the rent in the past? Have you discussed this with the person whose name is on the lease? I strongly suggest that you (at least) show up in court to hear what the plaintiff tells the judge and to be able to present your defense. In addition, assuming you know the "someone" who filed the claim, you might consider discussing it with that person, especially if you believe an error has been made.

A written lease is not required to establish a tenancy. Occupation of the premises in exchange for rent is all that is required. If that fits you, then that is why you are named as a defendant.