4chan party van
4chan Party Van
The 4chan Party Van is first seen in an MS Paint comic. Anonymous answers his door after the person knocking claims it's the "4chan Party Van", but unfortunately it turns out to be the FBI, who proceed to exclaim "LOL J/K" and beat up Anonymous.
4chan Party Van is now used as a euphemism for "FBI", often posted during child pornography floods; became extremely popular after the Jake J. Brahm incident, where /b/ became aware actual FBI agents might be monitoring their chaos. This newfound knowledge both excites and terrifies many /b/tards.