To preserve the functioning of WTO dispute settlement following the blockage of the Appellate Body, a sub-set of WTO Members created the Multi-Party Interim Appeal Arbitration Arrangement (MPIA). In the wake of the first appeal award rendered under the MPIA, this contribution describes how the MPIA process works and lists some of the innovations that can be found in the first MPIA procedure. More innovations can be expected as arbitration under Article 25 of the Dispute Settlement Understanding (DSU) (be it ad hoc or under the MPIA) can be adjusted and molded case-by-case by the disputing parties in their appeal arbitration agreements. In this sense, the MPIA can serve not only as an interim stop-gap to preserve WTO dispute settlement. It can also function as a laboratory to explore and test new ways of making WTO dispute settlement more efficient and in line with WTO Members' goals and interests: experimental reform by doing, rather than one-off, formal DSU review.