The Ghost Invaders are a group of ghosts who came through a Time Slip, created by the Ghostbusters, to 1959.
Due to an accident Peter Venkman caused with a Trap, the Ghostbusters and Slimer were transported back to April 10, 1959. However, their presence placed a heavy strain on the space-time continuum and tore a hole in the fabric of time. Ghosts came through the hole and terrorized New York City for an hour. Engine Company 93 declared war on the ghosts and fought them nonstop. Along with the Ghostbusters, they found the hole and battled the ghosts. They were pushed back and sealed up when Egon Spengler recreated the accident. The company was credited with stopping the ghost invasion and the Firehouse was declared a historical monument over three decades later in relation to the event.