I can't speak for all 50 states, but since I live in NY and have been sued in small claims court, I can state with authority that NYS requires that corporations be represented by attorneys in small claims court. In my case I was able to prevail on the judge to allow me to appear pro se, since I was the sole share holder, and the claim was less than what 2 hours of an attorney's time would have cost.

In the one case where I was the plaintiff, the case was settled before trial, so I don't know what would have happened otherwise.