Agent lists fictional company as plaintiff on landlord/tenant case and judge allowed it! Can I appeal to higher court?

Presuming the eviction case was filed in Magistrate Court, you have a de novo right of appeal, which means you do not have to show anything was done improperly in the trial court and the case starts over in State or Superior Court. You only have 7 days to file the appeal and if there is a judgment amount and an amount for rent per month going forward, you will have to pay those funds into the registry of the court to maintain possession of the property during the appeal. The agency issue is not likely a winning argument for you. You should at least consult with an attorney before you file the appeal. State and Superior Courts are formal courts where the civil practice act applies, unlike Magistrate court. Being pro se in Magistrate court is one thing, but to go pro se into the State or Superior Court will be difficult at best for a non-lawyer.