There is a one episode OVA that takes place after "Full Metal Panic! The Second Raid". It is a humorous stand-alone story. It focuses on the Captain of the Tuatha De Danaan: Teletha Tessa Testarossa, rather than the two main characters of the series. The OVA is based on short story "Wari to Hima na Sentaichou no Ichi Nichi" ("A comparatively leisurely day of the squadron commander") in short story collection "Dounimo Naranai Gori Muchuu" ("Helpless in the thick of it"). The story is also told in chapters 13 & 14 of "Full Metal Panic Sigma" manga volume 4.