Sanctus Mickey is a fan made antagonist in Abandoned: Discovery Island.
To activate the easter egg, press the Cactus Kid poster on the office, then in approx. 3 seconds you must shut off the power, when the power comes back on.
Sanctus Mickey will appear on the roof and then start to move.
After being on the Roof for a while, he will instantly teleport to the office.
Hiding under the desk will make him leave.