My own purposefully crappy theory.

In the source code, there's "INST". Institute. Gizmonic Institute. One of the employees created robots. His name is Joel Robinson. He got shot into space in MST3K. This mirrors how he is sad desk man and is killed. Source code also has Chica's Party World. Chica's Party World and, by further extension, Fazbear Entertainment are owned by Gizmonic. Silver Eyes has Henry make robots. Henry = Joel. Afton Robotics. Afton was Henry's constant enemy. Dr Forrester was Joel's constant enemy. Dr Forrester = Purple Guy. Purple Guy killed kids and put them into robots, making them murderous. Dr Forrester shoots Joel into space in MST3K. BAM.

TL,DR: Fazbear Entertainment = Gizmonic. Henry = Joel. Dr Forrester = Purple Guy.