SCP-878
The Actor
Connected to: SCP-1241
SCP-878-2, promotional image from ███████.
Special Containment Procedures
Efforts to physically contain either SCP-878-1 or SCP-878-2 have as yet been unsuccessful. It appears by all evidence that SCP-878-1 has no special abilities separate from SCP-878-2, though SCP-878-2 has shown a primitive sort of willingness to protect SCP-878-1. Their primary effect can be completely abated by disrupting distribution and broadcast of any media containing SCP-878; Foundation personnel will monitor television, film, or any other media containing SCP-878 for purposes of suppression. This has successfully prevented SCP-878's effect in 78% of containment attempts since discovery of SCP-878. Barring this, iterations of SCP-878-3 can be contained and prevented from harming others; this raises containment effectiveness to 95%.
Description
SCP-878 is an actor, alias "████ ████████" (SCP-878-1), and a prop knife closely resembling a 6th century iron dagger from the ███████ dynasty period in ███ (classified as SCP-878-2). SCP-878-1 has never had a permanent role on any television show, nor a role of any real importance in any film. SCP-878-1 appears approximately once every █ months on the set of various television shows, films, or theatrical performances during production; the crew forgets SCP-878-1 was ever absent, and alters the script to include "him."
After SCP-878-1's appearance, at some point throughout the course of the plot, the character played by SCP-878-1 will find itself in a situation that brings it into conflict with a more important character. The conflict will develop into blows, which always ends similarly. SCP-878-1 will beat his opponent mercilessly, far beyond both what is necessary to disable the character and beyond the level of brutality typically expected from the film or show in question. Once the other character stands for the last time, SCP-878-1 will strike the other character with the back of his left hand, leaving them sprawled on a desk or some other elevated surface, remove SCP-878-2 from an unknown location, then plunge the knife fully into the other character's heart. SCP-878-1 will turn towards the camera; at the moment his eyes meet the camera, the show will go to commercial or the film will change scenes. Alternately, during theatrical performances, SCP-878-1 will simply disappear, with no audience member able to recall where the character went. SCP-878-1 will not be seen again, and no explanation will be given for his absence.
From this point on, the actor who was "killed" may be identified as SCP-878-3. After the event SCP-878-3 will begin to display behavioral abnormalities uncharacteristic of their previous personality. This will begin with minor sex scandals and drug addictions, degenerating within a matter of weeks into paranoia and homicidal tendencies. If SCP-878 is observed at work, SCP-878-3 can be contained by Foundation personnel, though the symptoms will never abate and the actor will typically find a way to kill either others or themselves. Since most instances of SCP-878-3 simply "disappear" from the public eye, a fate not uncommon for less well-known actors, the correlation between SCP-878-1 and his effects has gone unnoticed by the general public, and a stress-related cover story is given to the actor's families.
To the extent that they are a single entity, SCP-878's motives are unknown. No records of SCP-878-1 appearing in any media without SCP-878-2 exist, and his real identity is unknown. Proposals for controlled use of SCP-878 as a means of containing broadcast based anomalies, such as SCP-1241, are currently under review.