Two users from the United States, (one from Indiana typically on Frontier, one from California typically on Comcast) persistently adding indiscriminate lists focused on "Background Muppets" or "Background characters" or "Muppet cameos" or "Not Featured Muppets" across a wide variety of articles related to The Muppets. Active circa mid-2015 to present (2017).
Batman villain whose whole deal is adding Background Muppets
In 2006, at the company I worked at during the time, a company-wide email was sent telling all employees to not vandalise Wikipedia from the corporate network after the NOC admin saw edits from our office egress IP.
