On that fateful day, in 2077, the Dwellers were sealed inside the underground bunker that would serve as their home for the rest of their lives. They found out what Vault Tec did pretty early on and assumed it was a mistake of some sorts. Things functioned as normal, with Dwellers creating their own entertainment to pass the time.
The Tapes were quickly buried in storage, until some youthful Dwellers uncovered them and were greatly amused by the campy nature of the terrible stand up routines done by the infamously bad comedian Gavin Hammond. They jokingly created a cult around the celebrity, who was long since dead, treating him as a figure akin to Jesus and preaching that he would return to us and inflict his bad jokes upon us again.
This 'cult' lasted a few months, until the joke got old and the tape, along with the bedsheets made for the robes and some old photographs of the 'clergy' went back into storage. They were uncovered again, one hundred years later and believed to be genuine.
The Dwellers were going through a tough time at that point, after Dogs devoured an entire scouting party on their first attempt on making contact with the outside world. Of course, nobody was old enough to remember that the cult was created as a joke and thus, everyone began worshipping Gavin Hammond as an actual deity.
The Dwellers have since been spreading their religion across the land, they have been looking for converts and human sacrifices, to offer to their lord. They carry copies of his joke books around, like one would carry the Bible or the Quran, reciting the jokes to everyone they encounter.
In Brothers in Binds, they encounter the Convicts of the Church of Blessed Sacrament. Things turn sour as they reveal their plans to sacrifice Harriot, a valued member of the community to Gavin Hammond. She managed to break free, killing a dozen or so cultists before she and Doug Fargo fled into the wasteland.
They are later encountered again as Casamir seems to have weaponized them, making them into suicide bombers and sending them running towards the school. A dozen of them are killed by either themselves or Blessed Sacrament Convicts, trying to defend themselves. It is currently unknown why they sided with the Copper Toes.
Brothers in Binds