John Margeret Skip
The John Margeret Skip, also known as Sen's Skip and 2BSkip (Sens Fortress Glitch), was an incident in the community involving a video by a YouTuber named John Margeret. In this video, an apparent method was shown that would have allowed to skip ringing both Bells of Awakening to gain entry into Sen's Fortress. After this video went viral, several big Twitch broadcasters attempted to recreate the method used in the video for several hours, though they all failed. At this point there were suspicions about the video being staged.
A later video also on YouTube by a different channel later repeated this feat, and after a little more testing by broadcasters it was once again concluded to be staged. It later revealed that both video authors worked together and the videos were either created using Splicing or using external tools like Cheat Engine.
Since then, an actual way to skip opening the gates to Sen's Fortress has been found, see: Sen's Gate Skip