You can do a signup all from other fandoms if you recruit your friends. (Or your frenemies. Or your flat out enemies, I don't care.)

You don't have to request or offer any fandoms from the checkbox list. Those are just the fandoms that I think, based on past experience, will have a fairly high number of requesters/offerers. (Admittedly, the more people include those fandoms, the easier it is to do matching.)

But sign up for what you want, and bring along some friends who share the fandoms you plan to sign up for. I really enjoy seeing more people participate!