SCP-[REDACTED], also known as "Mr. Fox", "Sir Reginald K. Foxington III", or simply "Sir Foxington", is a mysterious entity resembling a tall anthropomorphic red fox (Vulpes vulpes) with crimson red fur, emerald green eyes, a slender build with thick, wide hips. He wears aristocratic clothing, including a black suit that clings rather tightly to his body and leaves little to the imagination, a matching top hat, white gloves, and a fancy cane. He almost always has a smug grin spread across his face and a suave and charming, but playful and teasing, personality to match.

Mr. Fox's exact origins and motivates are unknown, along with the extent of his power. He mysteriously appeared one day at one of the Foundation's more secure sites, walking up to the highest-ranking officers seemingly out of nowhere before disappearing just as quickly simply by walking through the nearest exit. He has sense made numerous other appearances, having taken an apparent interest in the Foundation, and seems to enjoy messing with staff members of every rank and field, showing rather a mischievous nature.

The Foundation has since made numerous attempts to contain and apprehend him, to no avail, though attempts to glean information from him have proven surprisingly successful as he seems to enjoy interacting with staff members and is surprisingly cooperative in this regard (though male staff have noted that he can be a bit "handsy" at times).