SCP-5999 (a screamer video at the end of the article meant to be a memetic kill agent), SCP-3935 (the voice of a little girl says "hello" without warning if you stay on the page past a certain point) and SCP-035 (SCP-035’s expression changes at random due to the seemingly static image actually being a GIF)
Many SCPs break the fourth wall by directly or indirectly addressing the reader. Any article tagged “meta” or “pataphysics” uses this trope. Sometimes this is for humor, but more often than not it’s used for horror.