Stands for "Organization too secret to know"
Origin: Middleman Comics
sidekick is wendywatson
trained by sensei ping
When a job is too dangerous or too strange they don't call super heroes they call the MIDDLEMAN
Wendy Watson: where DO we get all the weapons and gear from
Middleman: Well ocasionally I get a parcel from O2STK full of weapons and inventions and....
Wendy Watson: Wait "O2STK"?
MIddleman: Organization Too Secret To Know