Never has the TMZ staff so quickly assembled for an outing ... lining up to douse Harvey over ... and over ... and over.
More than a dozen staffers double-fisted sippy cups filled with the cold stuff for the ALS Ice Bucket Challenge.
When the cups were empty ... the staff wanted more ... staging a coup.
The challenge has been the most successful campaign in memory, raising almost $23 million.
You gotta watch the video and hear who Harvey nominated for his challenge.