Sew thread through your top hat and to the top hats of other people you know and you'll turn into a group of top hat wearing people. You're all connected by the thread now, so everyone will assume you're a group, even if that's all you guys have going for yourselves.

Everyone in this group loves cumin (くみ). You know, the spice or seed. The group take off their top hats and fill them with cumin. You're officially a group for lovers of cumin.