Civil War banners
Origin
Marvel had a Civil War marketing campaign that sucked and everyone lampooned it.
Significance
Mocking comicbooks, particularly comicbook 'events', is excellent parody fodder. Many SDN users still use these banners.
Stupid People
Frequently, new and lazy users will ask what these banners/references mean, rather than reading the FAQs.
This includes:
Darth Ruinus, 6/11/2007
--Stark 02:11, 6 November 2007 (EST)