Miguel Caldera was a programmer working for Vault-Tec Corporation before the Great War. Burdened by soul-crushing office programming jobs, he longed for nothing more than to live in the country and focus on hiking. The Great War made that dream come true with a vengeance. After taking to the woods, he survived for several years in the wilderness, until he was severely injured on the trail, just barely making it to the Flatwoods outpost circa 2093. After Responder doctors stitched him back up, Miguel found his new calling and became a volunteer Responder himself, acing their survival training programs. He believed that the threat posed by the scorchbeasts meant nobody was safe anymore and being a part of a faction that has everything figured out meant he could help.
As a programmer, he became a boon for the Responders, helping the struggling faction create automated training kiosks to expedite recruitment and processing of volunteers, as well tackling the daunting task of maintaining their Protectron fleet. He also helped train others in camping and survival, leaning on the years of experience he accumulated since the war. His first major personal achievement was the creation of Mr. Fluffy, a bodyguard and assistant. The robot, stitched together from countless damaged Protectrons, had an attitude problem and was none too pleased by its name (metallic surfaces are by definition not fluffy and the failure to computer aggravated his neural network).
On top of the classes and programming, he helped ferry supplies to Flatwoods. It was during his many supply runs between Morgantown Airport and Flatwoods that he met Garry Wilkins and fell in love with him, to the point of deliberately planting bugs in the kiosk software to get an excuse to visit the outpost and Garry more often (much to the chagrin of Dassa when she found out while recovering her Survivor Stories series). Eventually, Miguel transferred to Morgantown Airport with Garry, in order to devote his time to lead Advanced Training classes on survival and camp building, on top of his engineering and programming duties, while developing a reset program to make Fluffy a little more conventional, rather than loom beside and over him all the time - ruining his sex life.
However, no matter how much the Responders tried, the casualties just kept rising and soon even Miguel started to doubt the future. He resolved to taking a day off to help him get his bearings and enjoy a night together with Garry... Except it would not come to pass. Garry would be killed a few days later when a scorched rushed past the gate. After burying him on the hill , Miguel left Morgantown Airport with fluffy to make camp, clear his head and, by all appearances, take his own life.
Miguel Caldera appears only in Fallout 76.